Pietta mfg - the FAP in a diamond,
Are you certain it is a Navy Arms gun? AFAIK, Navy Arms (at least at that time) always had their guns made by Uberti, and my three all have the Uberti trademark as well as the Italian black powder "PN" proof marks*. The second picture shows a trademark used by Replica Arms, not Navy Arms.
Note that absence of Italian proofs indicates the gun was not assembled in Italy. If the parts were made in Italy and assembled elsewhere, the gun was not proved in Italy so there are no proof marks.