The 'free' Helios 103 53/1.8 that came with the Contax RF adapter.
My homemade adapter for Ricoh breach mount lenses. A Fotodiox 7mm extension tube, a 52mm Skylight 1A filter with the glass removed, the mount from a broken Anscomark M, and some Loctite Fun-Tak...
The 7mm tube was just a little short, the 14mm tube was too long, I discovered by accident that the Fotodiox X mount tubes were 52mm...the de-glassed filter added just enough to the 7mm. The internal mount from the camera is just a little wider than 52mm, maybe 54 or 55mm, so it fit over the top of the tube, the Loctite holds it well enough and is reversible...I think RioRico would be proud...even if I didn't use a Dremel...