>>Benjamin Franklin 312<<
The "Benjamin Franklin" is in quotes it's a play(joke) on the company name of Benjamin Air Rifle Company. There is not now nor has there ever been a Benjamin Franklin airgun Co
"Benjamin Franklin" - Benjamin Air Rifle Co
http://www.pyramydair.com/blog/2009/08/benjamin-front-pump-pistol-part-1.html
If you scroll down to the first photo, there is an explanation of "Benjamin Franklin"
>>Where to get a Benjamin 312 worked on?<<
http://www.pyramydair.com/blog/2005/07/co2-and-pneumatic-guns-where-to-get.html
Tim McMurray - Mac 1 Airguns
310-327-0238
http://www.mac1airgun.com
George Pena - TX
512-863-2951
heligun1@msn.com
Rick Willnecker - PA
717-382-1481
airgunshop@aol.com
All repair old Benjamin pumpers
Airgun forum
http://www.network54.com/forum/79537
Old Benjamins are very popular, you might do a search(old questions/answers) or ask for a reference on this site for someone in your area. But, I do know that the three above are all well thought of and that Tim McMurray is considered to be one of the best in the world.
I had a old Benjamin 312* when I was a kid and when I heard about the new model 342 I put in my order at the Coast to Coast hardware store in our little town. That was 1969 and I believe the rifle cost $29
*a friend of my grandmother gave it to me, in exchange for doing some work for him.
Good luck