The M&H was reasonably popular. I don't have a large frame one, but do have ones in .38 and .32. They don't work quite like most folks think.
First, the idea was that when the gun was opened the gap between the cylinder and the breech face was just a bit longer than the case. When the cylinder is pulled forward, a ring in the breech holds the cases back. Empty cases drop free, while the bullet in the barrel retains unfired rounds which are returned to the chambers when the gun is closed.
That means that the revolvers made specifically for M&H rounds won't work right with the shorter .32 S&W and .38 S&W cases.
Also the guns are slow to reload. They can't be reloaded while the cylinder is forward as the case rims won't go over the ring that holds them. Instead, the cylinder, partly or completely empty, has to be brought back and locked. Then the downward sliding loading gate has to be opened, and the chambers loaded one at a time, just like the Colt SAA. When rounds are loaded from the rear, the rim is held by the fixed ring in the breech face. There is some speed gain over the Colt, but the gun is nowhere as fast to reload as the S&W topbreaks. The advantage, much advertised, was that only the fired cases were extracted.
In practice, that didn't always work, either. The cases are all extracted, but not ejected, so that empty cases can be stopped from falling away by loaded cases below them. Still it is a neat system and the larger frame guns are now quite expensive. The smaller guns can be obtained quite reasonably, and one in poor outward condition but usable for study can be bought for around $200 or so. (M&H were marketers and patent holders, not manufacturers; the guns were made by Hopkins and Allen. Quality, as one would expect from H&A, is excellent.)
Jim