I read that somewhere else as well. I've gone over it with a flashlight and a magnifying glass, twice. I cannot find a box with letters in it. The SN starts G47...To find the build date, look for two letters in a box somewhere either on the receiver or around the trigger guard. If it is older than 1975 it will have a Roman Numeral type date code. Beretta USA list them, but if you could find the stamping I can give you the date.
No joy. Their system doesn't recognize it.Try plugging your serial number in here: Firearm Technical Data