As JohnZ has stated, D.R.P on the (metal part) frog is patent related, DRP on the blade of bajonets (mostly WEYERSBERG or ALCOSO) is postal related.
Postal protection force related frogs do have very special stampings.
Regards,


wotan, gd.c-b#105

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