I am seeing an R with a Crown above it on both barrels.
According to Steindler's translation of Wirnsberger, page 38: "Article Four covers alterations of an already proofed firearm. These changes [alterations] can occur in either barrel, such as rechambering for an improved cartridge, or a change in the action or magazine so that the gun will handle a cartridge of a caliber different from that for which the gun was proofed. In such cases, the gun must undergo proof again, even if the barrel[s] has [have] not undergone any changes and has [have] retained its [their] original caliber [gauge]. The mark for such re-proof is Crown/R."
The gun's having been proved for Nitro powder could account for the surplus proofmarks.
