Barrel flats. K.M.G. = Copper metal jacket bullet at 19 gr x 15.432 = 294 grain bullets.
One can see the fine joint between the chopper lump barrels. Split ejector actuators.

Date stamp 11/25.
Correct me on the German proofs: Crown over N is the Nitro proof. Crown over U is the barrel exam .
Crown over G is for rifled barrel and crown over R test after repair. 10 mm is the caliber.

Arm and scepter over NP at 16.5 tons is the British nitro proofs of .405 x 2.58 case length.

Breech face shows the bushed strikers and side clips.

Here is a sample of the borderless checkering on the grip. Very little wear.