Did not see this posted here. Very impressive work. I assume they install or sell these, but not sure. I guess good news, New metal Clearing rings are available.
https://www.curta.fr/pannes/fabrication-d-un-anneau-de-remise-%C3%A0-z%C3%A9ro/

Very interesting, thanks Davhamm! Sounds like it's time for me to offload all these plastic rings I had made then...

Thanks for your comments Pete and davhamm.
Right, I can install a new clearing ring on Curta if asked for and can do some other works.
Nevertheless working with US is a little difficult, due to the distance. I mainly have works with France and sometimes with european countries.
And I also collect Curta.
Regards,