J. Stevens is probably 1920 to 1940. No serial numbers were required in those days. In good condition, value (although you didn't ask) is $120-150. There is no need to disassemble it. You can clean the barrel from the breech end. Just a guess, but that knurled screw under the forearm will probably allow you to take the action/barrel out of the stock. Looks like a nice little .22. A great gift. Google J. Stevens .22 bolt action. There is a lot of information out there.