From 1945 into the early 2000s, Beretta used a stamped inside a rectangular box on the frame or slide. This code is separate from the serial number.
The location depends on the type of firearm: baretta serial number lookup
Confirms the exact variant of your firearm. From 1945 into the early 2000s, Beretta used
Here is a guide on how to locate the serial number and what a lookup can tell you: From 1945 into the early 2000s