Thanks for your comments.
One of the things that popped into my mind is that it would be really cool to have Block time there, either instead or along the "normal" time.
I agree, it would be incredible.
"Bitcoin is time" is a great article by "der Gigi"
https://dergigi.com/2021/01/14/bitcoin-is-time/I see some similarities between btc and a mechanical watch: Energy, time, proof of work,... can't write an essay.
Amy plans to make a series for the public
I can ask the watchmaker, but it would be a bit expensive more than 1'000 CHF.
I am still not sure if it's smart to put the priv key in the movement. makes sense for waterproofing, ... My first idea was to put only the Bitcoin address on the dial. But need more tests with the qr code, so that it is readable. and not sure about generating priv key and then engraving it.
Can I pay you by sending some money with snail post?
Send it. you get it.

Thanks for your inputs...