This, I believe, is all of the half frame cameras I have. Most of these I have used, but not recently. Starting from the front and going clockwise, is the Olympus Pen FT, the Canon Demi S and then the Bell & Howell Demi, practically the same camera as the Canon except for the lens, the Bell & Howell Dial 35 with wind up motor drive, the Yashica Samurai X4, and then the Mercury II. Of course my favorites of these were the Pen, the Dial, and the Samurai. I made a good bit of pictures with these three.
The Dial is an interesting camera and worked fine mostly. It was a little bit finicky in loading film but did OK after that. The automatic setting worked for me most of the time.
The Mercury II looks really "classic". Beautiful camera. Half frame is an interesting option. I don't have any yet, but I nearly bought a Fujica drive recently. I refused just, because I wasn't sure, if the light meter was still working. Any example pics ( taken with those cameras ) of your nice half frame collection ?
If you are seeking the Univex Mercury, don't forget the US made Mercury 1 does not take conventional 35mm Kodak type cassettes, it used a system rather like the Agfa Karat and Agfa rapid, Robot, or Bessamat, where the film goes from cassette to cassette. The Mercury II was a later modified Univex design, and added normal Kodak 35mm cassette fitting and rewind.
Both use a cine camera style shutter, a rotary unit, that is quiet and quite reliable. They have interchangeable lenses, but these are very rare indeed.
The top of the rotary shutter has the infamous exposure guide on an engraved plate at the back of the body, very comprehensive to say the least!