ENM: First of all, no one has taken the time to welcome you to the site, so please accept this as your welcome.
You have a very nice gun there, obviously a higher-end piece from the engraving, etc. Not the typical engraving for a German gun - that would more likely have been figurative than the scrolls and such you have. So I will go along with this gun having possibly been made with either the export market or fanciers of American/English style guns in mind.
Now, on to the questions.
First, I'm a little dubious about the state of the receiver. Most receivers of that vintage were color case-hardened and yours appears to be a relatively uniform dun blue color. That uniform coloring would not necessarily exclude the gun being unfired (or only lightly used), but it raises a question: was this gun re-hardened, used and blued, or did it come that way?
Second, I'm left to wonder exactly what it is that is on the face of the right barrel's standing breech (where the firing pin protrudes) and also in the angle between the standing breech and the watertable. In the angle, it appears to be rust, and a lot of it. On the breech face, it appears almost like someone dropped a bead of weld metal (or other metal) on it. That corner is a very bad place to have rust or damage as it is one of the highest-stress points during firing. So we need to hear and see more.
Third, I'm a little dubious about exactly what the patterns of light and shadow on the receiver's watertables are from. That area is almost never anything but plain and flat, with required proofing stamps the only markings. Your pictures show odd shapes - they could be from some episode of heating or something else.
Without more information on what's going on in those places and with the color of the receiver, it's impossible to give an estimate of the price because it's really impossible to know what the actual condition (and history, as reflected in condition) of the gun is. The quality and coverage of the engraving points at a higher value, but if the mechanics are bad or compromised, all the engraving in the world won't change that.
This is one, IMHO, that needs an in-hand inspection by a really good smith experienced with doubleguns or a very knowledgeable prospective buyer.
And, as noted above this was a Simson gun made under the BSW name, sold through a retailer in Berlin. Interestingly the proof date of 7/36 means it may have been made in anticipation of the Olympics of that year to sell to visitors to Berlin in that time, but that's just speculation on my part.
Last edited by Dave in Maine; 02/03/19 11:18 AM.