Hi Christian,
That looks like a nice 105.012 you have there. Difficult to tell for sure without taking the back off but I'd say it's a -65 or -66 in almost original condition. The red hand is obviously an issue and is probably nothing more than a previous owner's "fiddling". I'd see if you can remove the red paint and see what it's like underneath. A nice tritium chrono seconds hand isn't too easy to get but not impossible.
As you say, they are pretty robust and a little tlc will bring this one back to order if you want to. Funny how folk still worry about living with a hesalite Speedy, this one is testament to the "wear it and forget it" philosophy.
Cheers - Simon