see <http://media.winchesterguns.com/pdf/om/model1200_om_s.pdf> and/or <http://www.YouTube.com/v/cDAhWKmHamI?version=3>
I believe that your Sears shotgun is a Winchester model 37A shotgun that was made for Sears Roebuck And Co,.
http://www.histandard.info/PDF/Sears%20Shotguns.pdf
sears roebuck and company
Its a Sears branded Mossberg 500.
The value of a Sears and Roebuck 12 gauge shotgun model number 281512651 depends on its condition. This gun in excellent condition is valued between 100.00 and 135.00 as of 2014.
http://www.histandard.info/manuals/sears/pashotguns/index.html
Winchester 1200
1952 by High Standard for sears& Roebuck
$49.95
Sears Slug Model 446.511761 is a Mossberg 500. All parts interchange.
http://www.histandard.info/PDF/Sears%20Shotguns.pdf
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.