I got my (new to me) 1966 constellation. It doesn't have hacking or quick date. It came as date 22nd and after much turning I got to 8 and the crown popped off and went flying. Found it and re-attached and then lost it again at work.

How can I get a replacement and prevent it from coming off? I think I unscrewed it somehow with all the date adjustment. Watch runs but can't adjust date until I fix it.

Incidentally what is this watch worth assuming I get the crown replaced?

 

You should fix your crown with loctite or similar.

Seems you need crown 42522ST=> £20 at cousinsuk

 

Welcome @Happy Highwayman

Nice watch, in decent condition, good lugs and a nice cross-hair dome dial - congratulations.

Well, the good news is that it looks like your watch didn’t have an original ‘hidden’ crown, so no tragic loss.
Probably replaced at service in the past, along with the cyclops crystal.
I would personally find a watchmaker to fit the replacement crown unless you are used to working with watch movements.


BTW - when you get the crown refitted, the cal 561 is ‘semi-quickset’ in that you can adjust the date by winding between 12 and 9