John, glad to see you were the one that won this gun. I have it listed on GB three separate times. 1918 would be the year. All hammer guns made at this time have the "H" prefix or suffix. The "F" grade stamp was not used because of the Field Grade hammerless guns, so Hunter Arms used an "H" to separate them in the ledgers and in catalogs.
I know you will enjoy shooting it as many of our members shoot L.C. Smith hammer guns. Royal Steel barrels are very strong even though they were the cheapest made when they first came out (Damascus steel was harder to make) I would the have the gun looked at by someone that knows L.C. Smiths and if determined safe would shoot loads under 8000 psi and 1200 fps. As mentioned RST is a good shell and if you reload they are hundreds of safe loads.
Good luck with it and let us know how you make out.