This Large "mini cooper" car
is actually storage for tiny cars, examples seen in foreground. Son has not played with it in years and we want to pass on to a younger boy, but can't remember how to open (without destroying it).
It works sort of like a transformer, has to be done in certain order, but neither child nor adult has had any luck with it today.
The two avenues I can imagine help coming: either you have/had the same toy and know how to open it, or you can help remember what this line of small car toys was called (not Micro Machines). If I knew the brand name, I might be able to find something with a search engine.
The small cars are plastic, about 1.25" long, and have a metal bearing underneath that gives them some heft and helps them roll
The large carrier is about ten inches long and was made specifically for this brand of small cars. Stamped on the bottom of the carrier it says "Playmates Toys Inc. (c)2004"