The stamped-in code on a GM engine block is found on a number of places around the engine, but the most common location is on the passenger side ledge of the motor. The GM stamp is unique as it is engraved into the block as opposed to a raised casting.
In the 1950's, the engine code would also include the last two figures of the engine assembly date. Throughout the years, manufacturers would also change the location of the stamp. The serial number can be found in other places, such as on the flange near the rear of the engine or above the timing cover.
Suffix codes, which appear at the end of the number, were often used with different car models. When researching a serial code with just the suffix code, more than one car appear. The preferred way to research the code is to use all the casting numbers on a vehicle.
When a block has been previously machined, there is a chance the stamp number may have been erased. Because of this, some car collectors attempt to deceive the public by engraving a new serial number onto the engine. Fake serial numbers are distinguished by the number on the stamp. They can be disproven using a printed or online database.