Proofhouse.com has a store brand chart. 75-190 USD
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.
50-200 usd
It will be marked on the barrel, but that should be a 12 g shotgun.
Winchester
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
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.