I add a few additional photos of the Mauser 1900. Meanwhile I noticed also the stamp 1623 in the front part of the stock. All parts of the action and magazine carry the same number. I talked with my gunsmith about the whole project and we decided to restore the rifle as is.

By the way, the sagging of the stock is not suitable for any scope assembly, it was intended for iron sights. Beside that it would destroy the appearance of original action to a certain extend. I will leave it as near to the original as possible.