Let me start by saying the Sears model numbers don't tell us much. However if you find a Sears ad from their catalogs they will have the serial number
Full auto M16s have slightly different sears due to being select fire. If you drilled some holes and put some other parts in with it, that would make your gun full auto. It is fairly complex and doing the conversion is considered "making" a machine gun. There are also sears that "drop in" and are thus considered machine guns themselves. The making route is no longer allowed since 1986 and the ...
Levels 60-70: Sears Village and the Hollowed Sepulchre At 60, the Sears Village rooftop course becomes viable. With the Kandarin Hard Diary completed, you can teleport directly to the bank, raising XP rates to over 50K/hour. It's a chill method and finally starts earning you good Marks of Grace. The Hollowed Sepulchre - Starting at 62
Its the WINCHESTER copy that is known different internally. Something different/badly-designed about the Sears shell-lifter. Although I don't actually know whether you can just swap-in a known good Winchester part in place of the (tin?) shell-lifter in the Sears version.
Sears & Roebuck Model 45 / Marlin 336 | Page 2 | The High Road
Sears and Roebucks sold a lot of foreign firearms through their catalogs, he may have gotten it from Sears.The cost at the time would probably be around 4 to 5 dollars when Colts and S&W's were selling for 13 to 15 dollars. Many times Sears and Roebucks would discount their inexpensive guns even more.