The marking does not identify the gun maker; it translates as "Special rifle barrel steel". The proof marks give some information; the gun was made in the Suhl (Germany) area, along with millions of other firearms. (The Suhl district has been the center of gun making in Germany for centuries.)
The gun was proved for use with smokeless powder (crown/N); it also has the proof for choked barrels (crown/W) and the standard final or definitive proof (crown/U). The proof was done at the Suhl proof house (the oval and pick are part of the Suhl city arms and represent a shoe sole (Suhl) and the area mining industry). The "12 57" is the date of proof (December 1957) so the gun is not old.
For general information, many guns made in the Suhl area (and other gun-making centers) were products, not of a single factory, but of a cooperative, in which one company made barrels, another locks, another stocks, and so on. Since it would be difficult if not impossible to put all the names on the gun, they put on none. Some of the other marks may identify the name of the co-op, but I am not able to recognize or identify them. Hopefully someone else can help.
Jim