I'm not an expert, but I did some work on an H&R of my dad's.... hard to see from the pics - but looks like a .38 hammerless auto eject model... If we had a side shot of it that would confirm it.
here's a link to a site I found helpful. The fellow that posted much of the info at that site is no longer with us - but the information continues.... noodle around there and you may find more info.