You are correct. The M1 Hammer was a limited build (I think under 50 guns total) from Class Three Supply in Hermitage, PA. If I remember correctly the head gunsmith there was a man named Al Dewald?(been awhile not sure of spelling) The magazine tube caps were a custom machined design, and barely cleared the bottom of the barrel. You could get 3 2 3/4 shells in the tube, 1 in the chamber and ghost load 1 for a total of 5. They ran fast and kicked like mule, so to speak. I got the chance to shoot 1 at KCR back in 2001 during a demo, and it was an experience. I put 15 rnds of 00 buck and rifled slug through one. The last 5 rounds we did a "speed run" and I was able to get the last round off before the first shell hit the ground. I have a picture somewhere where it shows the third shell coming out of the chamber, with two still in the air. It was an impressive gun. Class Three went out of business several years ago after the owner got himself into trouble (not sure of the backstory). The business changed hands, and eventually went under.