How do Post Office Workers Handle Stamps?
May 11, 2010 1:11 PM   Subscribe

How do post office workers handle the insane amount of special stamps?

Stamps (at least here in Japan, and I expect in most of the world) don't have bar-codes or other machine-readable data. They are just stamps. However, an insane amount of special stamps are issued constantly: seasonal stamps, commemorative stamps, whathaveyou. These stamps (to my knowledge) don't expire, so any given letter might have, say, a forgotten minor commemorative stamp from 1997, or from 1982, or the like.

As such, as far as I can tell, post office workers have to either 1) be able to remember every stamp ever issued, or 2) just accept any stamp-sized piece of paper in the corner with a number as being a valid stamp.

1 seems totally unreasonable. 2 seems absolutely ripe for abuse (just print a random picture and number on a piece of paper, perforate the edge like a stamp, and stick it on an envelope, and you can mail something for the price of your raw materials - 1 cent (yen) or so).

Is there some other sort of system involved? How do post office workers identify stamps as being "real"? Or do they, even?
posted by Bugbread to Grab Bag (15 answers total) 3 users marked this as a favorite
Well, there's the fact that counterfeiting stamps is a felony, since they are essentially cash. That puts kind of a damper on things.
posted by kindall at 1:16 PM on May 11, 2010

I know that there is a weird scanner that the USPS can detect if stamps have been previously canceled (meaning you peeled the stamp off a piece of already delivered mail and tried to use it again, even if it doesn't have any visible postmark ink on it), so I can only imagine that a majority of the stamp-acceping is based on scanners.
posted by banannafish at 1:18 PM on May 11, 2010

Some (many?) stamps have markings visible under blacklight, at least in the US.
posted by Weighted Companion Cube at 1:19 PM on May 11, 2010

Many stamps encode information using Phosphor bands which appear under UV light. This allows for machine sorting. Google Phosphor banded stamp for more info
posted by bottlebrushtree at 1:21 PM on May 11, 2010 [1 favorite]

Various magazines have tested the postal service's stamp handling by mailing themselves letters with spoof stamps on them, with the correct apparent postage (i.e., the number in the corner) but without phosphor barcodes, to see which got through.

In 1993, Canadian satirical magazine Frank sent a batch that included a Ben Johnson commemorative stamp where he won the gold for Freestyle Doping (Johnson won the 100m dash at the 1988 Olympics, running against Carl Lewis, but was disqualified for failing a drug test afterwards). It also included one celebrating Quebec cultural heroes like Poutine. IIRC, most of them got through.
posted by fatbird at 1:28 PM on May 11, 2010

Screwing around with the US postal service is a federal crime, which dissuades a lot of people. I'm crazy cheap, but I don't mess with the feds.
posted by theora55 at 1:42 PM on May 11, 2010 [1 favorite]

Here in Canada, only people who mail a small number of small items use stamps -- everyone else does bar-coded postal labels or pre-paid postage or what have you.

So the risk/reward on counterfeiting stamps is small, given that it's a crime to do it, for a net benefit of like, 50 cents or so. Even if it were quasi-legal and you weren't going to get into trouble for it, is the return on investment for your time in creating a believable pseudo-stamp enough to justify the design work?
posted by jacquilynne at 2:17 PM on May 11, 2010

I couldn't find any confirmation that phosphor bands are used where I live, but all our neighbouring countries do, so I assume it's an ubiquitous system. Yet again, I learned something interesting today!

However, a recent incident has me wondering how tight the checks are that are in place.

The magazine I work for has several readers' contests every month. So, every month, heaps of mail arrive from participants hoping to win. All pieces of mail are sorted per individual contest and after the closing date a few lucky winners are selected. Nowhere is stated participants can enter only one postcard per contest, so in theory anyone can send however many postcards they like. In practice, no one does.

A while ago, the person responsible for organizing the contests' postcards noticed several entries for all the contests with the same childish handwriting, so she started counting them. The same persone mailed 50-60 postcards and envelopes per contest per month. Now, we easily have 5 contests a month, so it amounts to quite a lot of mail every month from a single person. My colleague was - given the childish handwriting - a bit worried all this mail came from a child or mentally challenged person, which was costing their parents, them or their guardians a substantial amount of money every month. She started collecting all these pieces of mail, while pondering what the best course of action was.

And that's when we noticed something odd. At first glance, the used stamps were always colourful seasonal stamps for a relatively small amount of postage, so the envelopes and postcards were adorned with a lot of stamps. But by giving all these pieces of mail a second look, it became immediately apparent: those weren't real stamps! This person cut out pictures of stamps from post office brochures, used small supermarket coupons (that look like stamps) and stickers. We have no idea how many pieces of mail this person tried to send, but an average of 250-300 pieces reached us each month. Maybe 10-20 of those were marked "insufficient postage".
posted by lioness at 2:30 PM on May 11, 2010 [13 favorites]

The three different kind of (US) stamps I happen to have with me here all have UV banding (or in one case little flecks, like money), so that seems very common, and it UV ink is expensive enough that that seems like about the right amount of prohibition to me.

Lioness's story rings true for me too. I have mailed letters without stamps (forgot) and they arrived fine, and I have received more than a few without stamps, or with grossly inadequate postage. I think it's a high fail-rate system, and they catch and stop just enough to make mailing with bad postage unreliable, which is enough of a deterrent.
posted by rokusan at 2:57 PM on May 11, 2010

I know that there is a weird scanner that the USPS can detect if stamps have been previously canceled (meaning you peeled the stamp off a piece of already delivered mail and tried to use it again, even if it doesn't have any visible postmark ink on it), so I can only imagine that a majority of the stamp-acceping is based on scanners.

Anecdotally, my mail man says that he "re uses" stamps that don't have visible postmark ink on them, and everyone at his office does, too. And my Mom has the habit of painstakingly peeling off and reusing all postage that doesn't have ink visible on it, and in 50-odd years it has never been sent back, or (to her knowledge) arrived with more postage required from the recipient.

I was wondering about the same thing too, recently, given that you can now print personalized postage with photos or images of your choice on them, how do you check to make sure they're valid? Our postal worker's response: "I don't check them. I just put them in the bin."
posted by arnicae at 4:16 PM on May 11, 2010

The USPS uses a (pretty neat) automated system, called the Advanced Facer Canceller, to cancel stamps. It's essentially a machine-vision system that "looks" for a stamp on the front of the mailpiece using a UV (254 nm?) light source and camera, and then cancels it. The cancellation is done with UV-reactive ink, and the system is smart enough to recognize a previously-canceled stamp and not do it twice. The system in its most recent configurations also does a lot of other stuff, but the stamp canceling is sort of its core functionality.

From this page:
The USPS has a fleet of 1086 Advanced Facer Canceler Systems (AFCS) at USPS Processing and Distribution Centers (P&DC) throughout the country. The AFCS is a mail handling system that faces letter mail by locating the stamp, meter, or indicia. The AFCS also cancels letter mail, sprays an identification (ID) tag, lifts the image, and sorts letter mail to a set of bins for further processing. Individual mail pieces are picked-off at the Feeder of the AFCS at a throughput rate of approximately 36,000 mail pieces per hour.
Someone who tried to casually counterfeit stamps (using a laser printer and Avery labels or something else stupid) wouldn't fool the machine -- it wouldn't see the "stamp" because regular label stock doesn't look the same under UV as actual stamps do. The mailpiece would get kicked out of the machine and a human would examine it, and they would probably (hopefully? maybe?) detect the forgery. Incidentally this is why you get warned not to use Scotch tape over your stamps -- most kinds of tape are only transparent to visible light, and opaque to UV, thus the mailpiece gets rejected. It's also why, if you have a meter, you need to either use special stock (if it's a thermal printer), or use special ink (if it's a traditional inked-die printer).

I think the UV sensing system is actually less for forgery resistance (the special ink or stock for meters isn't hard to get) but to keep the automated canceling system from putting cancellation marks on things like return address labels, March of Dimes seals, random stickers that people put on their cards, etc. I'm sure it's possible to fool the system if you were suitably inclined -- it's just that most people don't care. If you have the chops to forge stamps, there are certainly more profitable things, illegal or not, that you could be doing with your time.

The only kind of stamp forgery/counterfeiting I've ever heard of recently was someone counterfeiting rare stamps and then selling them to collectors. This is not really that uncommon, and has a long history. It's a very different crime though; it's the difference between counterfeiting nickels for use in the office vending machine and counterfeiting a single really collectible nickel and passing it off to a collector.

250-300 pieces reached us each month. Maybe 10-20 of those were marked "insufficient postage".

This is interesting. I'm curious, if you still have any of them, whether the cancellations on the pieces that did go through look different from normal cancellations. In particular, do they have round hand-cancellation marks on them? My WAG is that all the mailpieces with the fake stamps got kicked out of the AFCS, because none of them would have looked like stamps to the machine, but that someone downstream of the machine must have decided to let them go through anyway. I'm surprised but I have no idea what the de facto policy is for stuff like that, or how common it is.
posted by Kadin2048 at 4:32 PM on May 11, 2010 [2 favorites]

I wonder if those pieces of mail are being taken in at a small town post office and hand-canceled ahead of the processing machines? You'd think a small town postal clerk who was hand canceling the mail would notice the fake postage, especially if it formed a significant part of their daily volume of outgoing mail, but maybe not if they had a lot to do, or maybe they do and just deliberately don't pay attention for some reason?

I don't know how most postal systems process mail from small outlets and small towns anymore, but back in the 80s when my mother was a small town post mistress in Canada, she hand stamped the outgoing mail every day. So by the time it got into the sorting and processing machines in a larger center, it would already have been canceled and the assumption would likely be that the postage had been checked at the previous step. She sometimes let me do it, because, despite the fact that letting me do it was apparently really, really not okay with the post office, listening to me whine about how I wanted to do it was worse.

I can almost guarantee, though, that even as a child, I'd have noticed badly faked stamps like the ones lioness describes. Most stamps that I saw were exactly the same as most other stamps that I saw -- because the small post office kept only a small supply in stock, and people bought most of their stamps there -- and anything that wasn't one of the 4-5 usual stamps would have attracted my attention just because I liked looking at them. I'd have noticed the different paper, the lack of perforated edges (though that indicator went away with the rise of self-adhesive stamps), etc.

(And if you think my mother letting me do her job was terrible, you should probably not click this link to find out what my father once let me drive at his work when I was a child.)
posted by jacquilynne at 5:24 PM on May 11, 2010 [1 favorite]

Yeah, if you think some pension-approaching federal worker is individually glancing at every piece of mail, well, not sure what rock you've been living under. The system is hugely automated, and very few local post offices even do any real processing anymore. Most mail is picked up from a wide regional area and taken to a massive facility that looks a lot like this, and optical and digital systems do much of the actual processing including reading addresses. (If I want mail to get anywhere soon, I don't hand-write the address, ever.) This is one reason the USPS simplified its mail rules a few years ago to eliminate many oddball sizes of letter-class mail -- so the machines can handle more of it.

I once worked for a Bell+Howell subsidiary that made these machines. They had sold hundreds of them to the USPS, and their most recent client had been Brazil. They had test runs set up at the facility and to watch them in operation up close was pretty awe-inducing.

So there is a computer that looks at the stamp, and it has a database of all the valid stamps, and some built-in tolerances for tears and the like. If it can't read the stamp, it dumps it out for manual processing, and then of course the people doing that have personal knowledge of valid stamps and probably a reference binder as well. But even they aren't going to spend too much time on this job (I'm imagining throughput at 20-30 pieces a minute.) It's more of a deterrence system than an actual enforcement regime.
posted by dhartung at 12:03 AM on May 12, 2010

Response by poster: Thanks for all the responses.

I gather that UV ink is the leading tool used in the US. Any idea what other methods are used in other developed nations? I live in Japan, and I just checked my stamps with a UV light - no reaction on any of them. At least here, UV isn't used. Dhartung mentioned a computer with a database of all valid stamps attached to a scanner or camera of some type, but I can virtually guarantee that that isn't used in Japan, given the way Japanese spend on infrastructure.
posted by Bugbread at 4:20 AM on May 12, 2010

According to this page, the automatic cancellation machines used by Japan Post are manufactured by Morico Co. Ltd.
Morico first developed its original automatic postal cancelling machine in 1932. The business is the authorised and appointed manufacturer of stamp cancelling machines for Japan Post. Throughout the post offices of Japan, the company’s machines have been actively selling for 75 years.
There are some photos of their machines here, and more on Morico's official website (English version). The models described don't seem as though they have any machine vision; they just sense the leading edge of the mailpiece and stamp the corner. (This is basically just like any high-volume meter from Pitney Bowes, except it's applying a cancellation rather than a meter indicia.)
When a photocell detects the leading edge of a piece of mail, a single revolution clutch is triggered and in turn a die hub is operated. The Stampee M-102U automatic tabletop cancelling machine can imprint onto a fixed thickness of differing mail, such as envelopes or postcards, without any adjustments. This is due to the specially designed separating mechanism. Lastly, the G3 automatic postal cancelling machine cancels standard size letters and postcards. The processing capacity is 40,000 items per hour, and postcards and letters can be processed together.
So I guess someone must glance over the stamped mailpieces by hand before feeding them into the canceling machine.

I have no idea what mail volume is like in Japan or what percentage of mail uses stamps instead of being metered, so it might be that it's just not worth it to install complex systems like the AFCS.
posted by Kadin2048 at 9:02 AM on May 12, 2010

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