Depends on model and condition. It was not made by Sears, but by another gunmaker FOR Sears.
mossberg 500
High Standard
Your shotgun was made by High standard in 1960 for Sears. The model 21 was first introduced by Sears in the spring of 1958.
Your 12 g pump shotgun was made for Sears by the High Standard Company- it was their Flite King model shotgun.
The J C Higgins model 20 pump shotgun 583 55 was actually made by Sears. Sears and Roebuck & co. owned High Standard and held all the licenses for this gun .583 means House brand exclusive Sears product. 55 is the Sears code for the year 1948
High Standard. http://www.histandard.info/PDF/Sears%20Shotguns.pdf
In excellent condition, around $200. The only pump shotgun that Brwoning ever made was the BPS. Ranger was a brand name that was used by Sears and Roebuck. It was used on many utilitarian guns made by various makers. This gun was made by Stevens and sold to Sears to be marketed as the Ranger.
Shotguns sold by Sears through years were made by many different manufacturers. It is very difficult to determine value because of the many variables.
Proofhouse.com has a store brand chart.
High Standard http://www.histandard.info/PDF/Sears%20Shotguns.pdf
Your gun is a Stevens Model 520. Made for Sears, and marked with the Sears trademark of Ranger. Nice pump shotgun, originally designed by John Browning.
Sears never made any guns. They were private labeled for Sears by gun manufacturers Sears guns are usually almost identical to a manufacturer's model, but I believe this particular one was made by Hi Standard to Sears' specifications and there was no equivalent gun with the manufacturer's name.