What I could observe there are some -originals- which look very equal in stamping like the one shown by you and also some with have an obvious difference between the "DRP" stammping and the number. Might be caused 1. by the different makers WEYERSBERG and ALCOSO, 2. by different runs and 3. by differing care of the craftsmen. You also can observe that the stamps did wear down as I could observe original examples which eg. did miss the "I" line from the "D".
Fortunately up to now there are few fakes around which easily can be detetcted. Fortunately it is not tooo easy to fake them simpy by a stamp as certain complexe features are observable on originals.
Naturally it is the nicest thing to buy it out of the family of the former wearer, together with other (in details fitting) items of the postal protection service, together with the original documents and documentation.
Regards,

wotan, gd.c-b#105

"Never look for sqare eggs" as a late owner of an original FHH-dagger used to say.