I happened across an old drilling at a local shop and am curious as to just what it is and what it's value may be. I can find no makers mark on the gun. It is low 4 digit serial number. It appears to be of East German manufacture based on the info I was able to gather from the proof marks. If what I believe to be the date stamp is correct, it is dated may of 1905. I believe the proof marks indicate 16ga x 16ga x 9.3MM. The shop is asking $850 for it...is this a decent price? With no makers mark, is there any way of figuring out manufacturer of this? Approximate value???
I have found several pictures of similar guns but they all had the safety/selector mounted on the side of the neck, above the trigger group...this one has the safety/selector on the top tang and another slide lever along side the front trigger.
Any help/info would be greatly appreciated.

There was no East Germany in 1905. Gun looks like Collath design (could be wrong). 9.3x72R rifle caliber like 38-55 ballistics. Shotgun chambers likely 2.5 inches. They can easily be reamed another 1/4 inch. If bores are in good shape, and all else functions, price is good.

Not sure if this is a Collath...it has an underlever stacked over the trigger guard (Rouxverschluss). The Collaths I have seen have the lever pivoting under the forearm. The action design is different as well although maybe Collath used this design as well.
This is what I think of as a typical Collath design http://www.cabelas.com/miscell...-ga-x-11x65-mm.shtml although they did produce a conventional boxlock in the 1920's and 30's.

This looks like a popular Suhl design of the 1890-1930 period that could bought from a number of German gunmakers. It was my understanding that the underlever design was dropped in favor of actions that could handle more powerful cartridges.

This is most likely a German Guild Gun produced around the turn of the century, probably in Suhl, but could be many other cities. These guns used actions from one builder, barrels from another, stocks perhaps from another, and perhaps sold at the local shop if there was one.

Most likely a 9.3x72R, which is equivalent to a .30/30 or .35 Rem, and is a nice caliber for deer, pigs, and even elk at close range. It is probably a 16 gauge with 2.5" chambers.

You need experience in examining this gun to make sure the ribs aren't loose, the action is on face, etc. $850 is a damn bargain if it's in good shape. Don't touch it if it needs major restoration, unles you're willing to dish out 1-2K.