Ive found these before, though not for a long time! Its the vehicle build sheet listing the spec to which the car has been built. when you ordered your car from new, you
would be asked to specify electric windows, alloy wheels, radio, etc, this sheet will show these options fitted, plus many more that the customer would take for granted, type and quality, and colour of the carpet, colour of seat belts,dipping rear view mirror, type of spare wheel, any decals fitted, locking glove box, headrests, etc, type of things that would make your car a UK spec car, all of those codes are then tied up with your VIN (chassis No) and that how they can get the spec of your car through the VIN.. you should be able to find you chassis No on that sheet, or part of it at least.. if it doesn't match! then worry

I seem to remember these things turning up under the rear seat taped to the floor, or just pushed under the carpet, under the rear seat!
I think they were left there for the dealer, if they needed it..
now, everyone run out and see if ya got one

Tom