The Aubrey shotguns in the 1906 Sears catalog started at $13.85 and went up to $69.00 depending on grade and engraving. The cheapest had Twist or "Armory steel" barrels and the most expensive had 6 blade Damascus. They were advertised as having "all the improvements found on other guns as well as some that are not found on other makes" and were the pride of the Sears line with a 60 day free trial and a 20 year guarantee. All were 12g sidelock double guns with either 30” or 32” barrels and POW stocks. Models were as follows:
18 AS - line engraving Laminated - 13.85
20 AT - line engraving Armory Steel - 14.85
22 AD - line engraving 2-blade Damascus - 17.35
30 ALE - leaf engraving Laminated - 16.35
34 ADE - leaf engraving 2-blade - 18.85
50 ASE - fine line scroll and game scene Laminated - 19.35
52 DSE - fine line scroll and game scene 2-blade - 22.35
56 engraved 3-blade - 29.75
58 engraved 4-blade - 39.75
60 made to order 5-blade - 49.75
62 made to order 6-blade - 69.00
Pics are here
http://www.picturetrail.com/sfx/album/view/17474742PeteM might be able to narrow down the serial number for you. Please note the Model 18 had Twist barrels, but the S3C is probably 'S30' for 30" Steel barrels so I could be wrong.