Tim, We had a similar question asked in a moderated group and got this reply: Here is a complete list of Vivitar numbers as received from Vivitar. Francis in VT Dear Customer, We have the disignations they are: 1) Universal screw mount, Pentax etc. 2) Exakta 3) Nikon 4) Canon FL/FD 5) Minolta MD 6) Miranda Sensorex 7) Konika 8) Pentax ES 9) Miranda Auto Sensorex 10) N/A 11) N/A 12) N/A 13) Topcon 14) N/A 15) Topcon super D& D-1 16) N/A 17) Topcon Auto 100 18) N/A 19) N/A 20) N/A 21) Olympus OM 22) Pentax K 23) Fujica 24) Yasica / Contax So it looks like you are going to have to post a picture, or at least a link to a picture of the mount in question. Mike
I know this is an old post but I just joined this forum today and saw this question. Anyway, the Vivitar 2X-20 tele converter was for Olympus's short-lived FTL camera, which had a Pentax-style thread mount for the lens but with an additional little gadget that allowed wide-open metering.
