The Savage 340, Stevens 325, Springfield 840 were all the same gun except for some slight differences and were made by Savage. What does the stamp on on the 840 say? From the info i have gathered (and much of it has been conflicting, varible and confusing to say the least) from different sources is that Savage moved operations from Chicopee Falls Mass to Westfield Mass in 1960. That is about all the info on its age i can tell you right now. You can try different sites to search the age by the serial number if you can find such sites. I did that for a couple of my Winchesters, but i have not found such sites that have listings for Savage Arms. If you really are dying to know the age, a member here called EVOC ONE hooked me up with a phone# for a guy that could probably tell you. I would be glad to pass that # along to you, just say the word.