That is a fantastic gadget, both for fun and to learn the ingenous mechanism behind it, which looks simple once you've find out. Many thanks to @SavageRodent!
I had to rescale by a factor of 1.006 % (I think, just to add 0.2 mm more) the outer rings in the plane of the ring (xy if its positioned lying horizontally), otherwise it was really tight to fit the inner and outer ring and impossible to remove once mounted. I don't know if it's the model or my 3D printer calibration. Anyway, after a little bit of filing and polishing a little I got these fantastic-working cryptex.
Btw, I used PLA, from BQ.