I purchased a Sauer & Son SIDELOCK at Reno a couple of years ago for $600. It was a 12 Ga.
Another to look for are the Prussian Chas Daleys. They never made guns but imported fine German doubles for many years. I believe they had Sauer & Son, Schiller and the best (imho) the Lindner (often Americanized to Linder). Made for this country, they were usually 12 Ga, often in the black & white finish in Damascus, and sometimes in American Walnut. I picked one up at a show this month which is nearly mint, has a $2000. piece of Circassian walnut, and was dirt cheap because the owner only wanted to sell it as a wall hanger. "Cain't trust them Damascus barrels"
As has been stated before, many German guns did not have names or had only the retailer on them. No problem. There were only really good German guns until after WW2. They are the best buys out there.
Pete