I have a Meriden Hammerless single Bbl 12ga.
http://www.meridenfirearms.com/images/trap1.jpg

Sleak hammerless single shot,,not the 'Trap' version shown on the website catalog cut. No raised rib on mine and mine has POW style grip instead of the SG. Maybe that's what they refer to as the Pigeon Grip in the ad(?)
In parts now for some renovation, but hope to get the thing out for a run soon. Damascus bbl.
Kind of a unique action, it has a slide inside actuated by the top lever and a bottom plate on the receiver like most all SxS's.

We had a 12ga Stevens/Savage 220 as youngsters,,I remember it kicked like hell. But the oldsters insisted on Peters HV 2 3/4 Magnums in everything so that may have had something to do with it.