I don't have that kind of lathe but there is a lot of people knowing better russian language than english that might have tsb20. Try ask if you of course know rus. To help you i'll translate down bellow your last question to polish.

On the other hand you have already inner backplate screw measurements. You can try make it and match with your chucks. Here an english movie how to make it.





- Czy ktoś posiada wymiary oryginalnej tarczy zabierakowej do tsb20?