According to ref. I have that would be a High Standard M#200. Which was a pump made in 12 guage only.
your sears shotgun was made by savage arms.There model number was savage model 96.
I believe that your Sears shotgun is a Winchester model 37A shotgun that was made for Sears Roebuck And Co,.
No sn provided and there is no sn data for Sears.
Winchester
It will be marked on the barrel, but that should be a 12 g shotgun.
50-200 usd
I bought a sears 684 shotgun (12 gauge) at sears around 1979 , for $ 99
Winchester, same as model 1400.
Marlin High Standard made the Model 75 20 ga semi-auto shotgun for Sears http://www.histandard.info/PDF/Sears%20Shotguns.pdf
Stevens
You would have to list the model number of your shotgun,to identify the maker of your sears and roebuck shotgun,in order to get the correct buttstock.
http://www.histandard.info/manuals/sears/pashotguns/index.html