Mate, what if I said it was a Yashica Yashikor? Well at least the same as a Yashikor, and I doubt anything to do with Tomioka. I run a website, www.yashicatlr.com, which focuses on the development and history of the TLRs but also covers Yashica's first 35 mm cameras. Everyone knows that the YE was released with a 5 cm f/2.8 Yashikor and the YF with a 5 cm f/1.8 Yashinon at first, renamed as Super-Yashinon later. However, the YF is also found with a pretty rare 5 cm f/2 Yashikor and that is identical in every way, except in name, to your Leonon.
I would like to pretend that I am clever and noticed that first but in fact Awano Mikio (or Mikio Awano, I'm not sure) of the Japanese enthusiast's magazine, Camera Collectors' News, noticed it way back in 1985. Camera-wiki.org mentions little about the YE and YF but Awano Mikio's/Mikio Awano's name and/or Camera Collectors' News are referenced in quite a few articles about rare Japanese models.
The link to the lens on my website is Yashica YE & YF. There are a couple of pics I have "borrowed" from the net plus pics from Awano Mikio's article.
At this stage, I can't begin to guess the maker but this is the little I know. There seems to be two versions of the Leonon, both with same/similar aperture design. The "other" Leonon probably looks somewhat like the Topcors but the aperture is different with the Topcors using straight blades, albeit with 10 blades like the Leonons.
I would like to use your photos on the website if I could. If you are agreeable, I would need your name to credit them. My contact details are on the first page of the site Yashica TLR. If you want, I can provide a copy of Awano Mikio's article and translation.
