The Owner's Manual published by S&W does NOT give instructions for disassembly of the magazine, which MAY mean it is not meant to be taken apart. They DO mention cleaning the inside of the magazine by holding down on the follower, and using a swab to clean the inside.
You can download or request a manual via mail from the S&W web site
Try egunparts or S&W
S&W only made the Model 57 and 657.
You will have to call S&W to find out.
I have a mod 41 ser.# 137xxx and it was made in 1970. it has the cocking indicator. You can call S&W and they will tell you the date of manufacture and it,s free.
You will have to call S&W, goes beyond published data.
The Marlin 9mm Camp Carbine will accepts the S&W Mod 59 Magazine . Joe-R
I can't find any reference to a Stevens mod 320 however if it is similar to their mod 124 (12 ga, bolt action, 3 shot box magazine, 1950's manufacture) then you will not find an extended magazine for this gun. Stevens never made a 5 shot magazine for this gun and no after market companies would either. A 12 ga pump with extended tube magazine is a better solution.
Best left to a gunsmith if you don't have a manual. Go to the S&W website and you can download or order one for free
Call S&W and they will tell you when it left the factory. It could have been made anywhere from a week to a year before.
its a game, just called "Garry's mod"
Inside the crane area