I have an "engine" stamp set that I have had for approximately 50 years.. It is called 1/8", has numbers and letters.. Harbor Freight sells a 1/8" stamp set that is very close, being from China the numbers/letters are not quite as sharp as a set made in U.S.A.
When I worked in the auto repair industry. over fifty years ago, we regularly stamped new serial numbers into newly rebuilt engines.. Many old cars used engine numbers as a VIN, this being the case, the serial number on the new engine was supposed to be recorded with the DMV.. Generally this did not happen because an employee and/or the vehicle owner had to go to the DMV office to have the new number recorded..
Even at $1.50 an hour, time was money.. Ergo, that is why the engine numbers on a lot of the old cars don't match the paper work..