The Universal Focusing Mount fits the 65mm f/3.5 Elmar, the 90mm Elmarit head, and the 135mm Tele-Elmar head. It can be used with a dedicated extension tube for the 135mm Elmar and Hektor heads.
Their was a short focusing mount for the 90mm f/4 Elmar.
Also, a mount that would accept both the 135/2.8 and 90/2 lens heads.
EVERYTHING Leitz/Leica made was asigned a pronouncable five letter code name. These were later changed to five digit numbers. There are some accessories that were on the market long enough to have examples marked just one way or the other.
Then there were thread mount (we used to call them "screw" mount) extension tubes for the original Visoflex which later became known as the Visoflex I, and that was 22.5mm thicker than the II, II-A and III editions so Leitz made a 21.5mm screw mount tube which was used in combination with the one millimeter thick screw to M bayonet adapter, but the adapter was only five bucks back then and Spiratone would sell you a set of three for $10.
When the dedicated 22.5mm screw to bayonet adapter hit the market Leitz closed out the old screw to screw tubes for two bucks apiece. They were matte finish chrome while all the other screw mount tubes were black paint. Back then nobody worried "OH GAWD! What if somebody sees me with a chrome tube on a black lens?"
Then there was a little bayonet to bayonet tube, shiny chrome, and I think 7mm long. I don't remember why it was made but it was cute.
When I first got into Leica I was about 18, and the older guys hanging out at the camera shops would be babbling away in five letter code words like visitors from another planet. You weren't really accepted as one of the boys until you learned them all. You were also expected to know on sight all of the variations of every Rolleiflex model ever produced, what "f-synch" on a leaf shutter meant, and understand that the only difference between a #5 flash bulb and a #25 flash bulb was that GE made one while Sylvania made the other.
