If you own an early type 1 pin slider type Curta you are probably aware of the little rubber "mushroom" caps that are sometimes seen on similar machines.
Aside from looking nifty, and offering slightly better grip, these caps actually protect the pins from damage as the Curta is slid in and out of its canister.

My type 1 No. 4440 is a beautiful and unblemished unit except for the ends of a couple of the pins. This is disappointing, especially as mushroom caps are so rare.
In the interests of actually protecting against further damage (rather than authenticity) I have come up with my own solution. Would you believe kite spar end caps ?

I used caps with a 1.5mm internal diameter, for a nice snug fit.

They look fantastically good, don't interfere with the function of the machine, and don't cause interference when sliding it in and out of the canister.

Total cost to protect all of my pin sliders was ..... wait for it ..... less than 80 cents !! .... all I had to do was trim them to length and put them on.

The caps that worked so well for me came from http://www.skyshinekites.co.uk

If anyone has reason to believe this could somehow damage my Curta, please let me know.

After my flip comment to your previous post, I'd like to say, "Good idea", those caps are a good solution. I never would have thought of those.

With the advances in 3D printing I think someone might be able to make some of these up, though, actual 1:1 copies. I myself had a bunch of plastic clearing rings fabricated (I had two Curtas needing them, I had to do it) and they look and feel identical to the originals.

I don't think we're likely to see replica Curta machines in the next few years - but mushroom caps, clearing rings, and cases (plastic cases that is) are low-hanging fruit and will surely become available. Heck, I've already got the clearing rings if anyone wants to buy one.