How is a postage stamp authenticated?
November 13, 2006 11:00 AM   Subscribe

How is the authenticity of a postage stamp verified in the normal mail delivery process?

When mail is delivered, how is a stamp validated? There are so many thousands of stamps from so many different years, all of which are valid postage. Combinations can be made of different stamp types and values. I assume the valuation is done through OCR or image-matching with known stamps. Verifying whether it's a real stamp, though, must be an additional step.

Why can't I print any picture at all on glossy sticker paper and cut it out with "stamp edge" scissors from an art store? Or, if I can, why do people buy stamps?

The point of this question is not to figure out how to fake stamps - it's to better understand how the mail system works, and was prompted by the recent FPP about the absentee ballot stamped with the alleged 100k stamp. Differentiating between rare stamps and very good counterfeits isn't really what I'm curious about; just everyday verification.
posted by odinsdream to Technology (11 answers total) 1 user marked this as a favorite
I believe the stamps floresce under UV light. In more recent years with the self-postage services, they'd have to have scanners to authenticate the bar code-type things as they go through the sorting machines.
posted by dr_dank at 11:27 AM on November 13, 2006

from Wikipedia
posted by cadastral at 11:31 AM on November 13, 2006

I don't think most mailed items are inspected. AFAICT something with insufficient postage will be delivered to the addressee about 80% of the time
posted by winston at 11:46 AM on November 13, 2006

Yeah, just try putting too few stamps on a heavy item (mail something to yourself as an experiment, if you like). It'll probably get there anyway. If you went around putting unstamped letters into postboxes with impunity, I bet quite a few would reach their destinations.
posted by reklaw at 11:58 AM on November 13, 2006

cadastral, no offense, but I couldn't see anything in the wikipedia page you linked to about verifying the authenticity of stamps. Flourescent dye is mentioned, but in relation to tagging the entire mail item.
posted by odinsdream at 12:06 PM on November 13, 2006

And, yea, the barcode stamps you can print online aren't what I'm asking about. Verifying these machine readable items would be easy.

What's machine-readable about the wide variety of actual stamps, though?
posted by odinsdream at 12:07 PM on November 13, 2006

This ebay auction has photos of stamps under a blacklight. (The top left and top right ones are US.)
posted by smackfu at 12:32 PM on November 13, 2006

So I can't find a reference, but if I recall correctly... a few years back a Canadian satire magazine, Frank, created a bunch of joke stamps and sent letters with them through the Canadian postal system. Pretty much all of them made it through. They had pictures of various unpopular politicians, etc.

Also, FWIW, Canada Post has come out with a "unlimited" stamp. It has no face value, but is always good to mail a letter. Makes it easier for them to raise postage rates for letter mail without inconvienencing all those people who now have stamps that are one cent too small. So no validation necessary.
posted by GuyZero at 12:58 PM on November 13, 2006

posted by RobotHero at 4:36 PM on November 13, 2006

What's machine-readable about the wide variety of actual stamps, though?

Nothing (AFAIK). Other than perhaps whether a stamp is present at all. It's pretty much the honour system with random checks.
posted by winston at 7:51 PM on November 13, 2006

Years ago I heard an item on pubic radio (probably All Things Considered) about fake stamps. Apparently there is a group of people who are seriously in to making fake stamps. Not to cheat the post system, but...just because, you know?

The guest told of actually getting busted for mailing a letter with one of his own stamps. Postal inspectors, or Secret Service or some such actually came and had a talk with him. His delightfully boyish stamp was the "Worm Comemorative" stamp. LOL!

Sorry I can't help with the actual question, but felt this kind of added to the thread in general.
posted by Goofyy at 12:07 AM on November 15, 2006

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