Do you absolutely need an I-10? I've got an I-22 55 f2.8, two of them actually, one CLA'd by Yuri Boguslav of Fedka, tested good and are both decently sharp copies. I have the J-8 now and they just sit in my bag
Funny question. Where does the infinity lock lay while mounted? I have a I-50 Collapsible that misses the recess in the body to allow for using the infinity lock. I’m shooting a Bessa R.
You are right! They most likely used Elmar 3.5/50 as reference for Bessa R and even with it in the place, you need to release button as soon as you move from infinity otherwise it will bump to other end of recess. With I-22 without removing button max distance is 20m, no infinity!
Did you think about rigid Industar 50, 3.5/50? It's just bit bigger than collapsible I-22, but it does not have focusing "button" to interfere with Bessa R body. It's smaller than Industars 26, 61 and Jupiters 3 and 8.