At first glance, the DM Lefever and the Royal Gun Co singles share a lot of similaritys on the outside from what I can see in the pic.

Nice single bbls all around.

I have a single bbl hammerless Meriden 32" but w/o the rib on the bbl. So I guess it's not the Trap Gun, but they did adv one as such . It has a similar bottom plate type action as some of these do. Completely different from their hammer singles.