Thank you, red9! That’s exactly what I am looking for. I think the two engraved revolvers I provided links to are stylistically very similar. I believe your Frank Wesson Model 1870 pistol contains an engraving style that differs enough from the two I posted, such that Robert Bates Inshaw cannot thus be the engraver of these Model 1 Second issue revolvers.

Therefore, if appears that the engraver of both would be F W Martin.

Additional commentary or criticism is welcome.