What does my hidden vin-number mean?

some panels have generic numbers stamped in them, possibly a stock locator number.
Your VIN in the dash should match the hidden VIN if 68 and up. I would look under the package shelf also for a vin that late (73)
Prior to 68 it was an order number that should match the fender tag.
it might read like 72C02123456 72= Hamtramck C = December 02 = the 2 day of and the last are the VON (Vehicle Order Number).