Some bits of amateur information that might help those who look for parts in the future
Crystals
Our crystals are 29.6mm in outer width, 297 / 29.7mm non-armored generic ones fit, but obviously one should seek 296 / 29.6mm armored / ringed / gilted ones with domes as high as possible - especially day/date movements have slightly higher sitting hands, so they are the most challenging, ironically the most accommodating day/date crystals are cheaper than the shorter date-only crystals when you are buying genuine ones, this is probably because I bought all the cheap/short ones on eBay and those that listed afterwards just reference the highest price later on
😀 TL;DR: Hard to find aftermarket crystals that are both ringed, really high domed and 29.6mm - this seems to be why 29.7mm non-armored ones seem to be used which is probably less water resistant
The crystal ring is part of the look, sometimes crystals have this very ugly staining on the edges, it's usually because rust dyed into the crystal, it can't be removed easily, but replacing the crystal gets rid of it
I'm sharing my crystal press case holder design, it's specifically for C-Case Constellations 168.0**'s - since the domes are super high you need a lot of space, with this tool the plastic presses on the case rather than the gold/steel bezel and there's much space for the crystal to freely fall
https://www.tinkercad.com/things/2CmxTsrGif2-cool-trug-jofo
Removing is easy and seems safe, could be done even for a good cleaning, which will probably reduce water resistance by removing the gunk that formed to make a seal. Pressing it back is obviously more challenging, I'd say it's risk free if the stem barrel isn't in the way as most watches don't have it in the way. If it's in the way you can't get inside the case with a peg, as it will be pressing on that stem tube, you'll need to press on the caseback, so a bit more challenging to get a good fit for a safe press
Hands
Last bit of information is about hands, basically there are almost no directly buyable replacement hands that are ideal for our Constellation's - our hour and minute hands are shorter than other watches that use the 561-752 family sizing - when you buy replacement hands, you realise how much difference 1mm makes - they fit and they look good, but they aren't 100% right - even if you find a short minutes hand, make sure you learn the length of the hour hand too, it's usually 1-2mm longer
Just received some steel hands from Ofrei, got the minutes length right, but the hours hand is longer. Only the minutes hand length is reported, so you'll need to infer the hours hand size by measuring the photo. Dimensions are center of the circle to tip of the hand. I'm still going to use it as it's better than the original hands that the original owner got painted to increase contrast.
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If anyone gets an Omega authorised watchmaker service and gets their original hands in a bag, I'd like to buy them
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