I repaired a model 312 pump rifle for a friend awhile back and it also was stamped "Benjamin Franklin"
If I remember correctly it was just a play on words according to Tom Gaylord.
http://www.pyramydair.com/blog/2005/06/whats-it-worth.html
At August 01, 2005 6:24 PM, Anonymous B.B. Pelletier said...
" Yes sir, it does have "Benjamin Franklin" stamped on the left side of the receiver tube, but that is just a play on the name of the company - the Benjamin Air Rifle Company, which you'l find stamped on the end cap behind the bolt.
There has never been a Benjamin Frankin model. Many older Benjamin guns have that name stamped on the side. The fact that the name is in quotes indicates that it's not meant seriously."
BBGun Bob
[email protected]
S.E. Michigan
"Springers are neat,,One Shot One Bullseye"