Konica LTM Hexanon 50/1.9?

[milescl]

Many of these take 39.5mm filters. I just got one, and it is the same. I was able to find a 39.5 to 40.5 step up ring on AliExpress.

The change from 39.5mm to 40.5mm filters happened somewhere in the #3,12x,xxx range