While this one is nicer than the "suicide special" that is what it is, I suppose. It's family history in a macabre sort of way. Because of that, the exact type really doesn't matter except as edifying knowledge. Aside from the US Revolver grips, it looks alot like the US Revolvers I have seen. The Secret Service special has a pin just below the rear sight, doesn't it? Though I suppose not all of them will have it. I'll defer to those who know better, though, because I'm more of a Hopkins and Allen guy (based on my family history, a whole lot more positive than yours).
But history is what it is. It might be really sinister to keep such a thing, but family history it is all the same.