I picked up a 1977 400 and the pad is stamped.

7T400
E
3

I know the 7T is for 1977 Trenton and the "E" is for cast crank but what is the "3" for?

Now here's the strange part, the engine has never been apart and the carb is a 9103 which is a 1977 400 HP.

I thought I read somewhere that some HP engines were just stamped with a number 2 or 3 instead of HP.
Is there any truth to that?