N&W,
According to my data, you are correct. The engine started life as a H8sc and upgraded to an H9sa (with snifter valve) although the upgrade per my data was done 8/1915. It was scrapped 8/1949. This engine never was a H10, and #7109 was not used again (the number was first used on a 0-4-0T built in 1879).
There was an earlier post that mentioned Lionel used three numbers for their "H10" release that were on H9s but never on a H10. As I have mentioned before, I think if you buy these "H10" engines that once on your layout just call them H9s because that is what they really are.