Locating the Serial Number on a Model 350A Shotgun

Question
just wondering where i can find serial # on this old gun my dad was handed down by my moms uncle?

Answer
Depending on when it was made, it may not have a serial number. Numbers were not required before about 1964, after President Kennedy was shot.

so guns made before then will not have a number.  The gun is still legal and all guns made before ser numbers were required are kind of grand fathered in.  If you wanted you could get one put on, but I would not worry about it.