No sn provided and there is no sn data for Sears.
Try e-gunparts/used to be called Numrich arms/It's on the web
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,.
50-200 usd
Winchester
It will be marked on the barrel, but that should be a 12 g shotgun.
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
http://www.histandard.info/manuals/sears/pashotguns/index.html
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.