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Vintage Omega acrylic crystals...

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Some of us probably have one or two vintage omegas with acrylic crystals and they are usually a hassle to work with because the crystals are not easy to find and the aftmkt is not much help.

So...here is a little bit of info on them:


You can use the Otto Frei website for omega crystal part numbers because it is accurate and easy to use:
For regular 'snap in' type crystals, I measure the crystal seat outer diameter and go from there.
'snap in' = the type of crystal commonly referred to as the GS brand PHD type.
Example:  If the crystal seat is 30.0mm in diameter the proper crystal will be 30.1mm or 30.2mm and they are installed using a 'crystal lift' or a press that has a cup with a tapered inside edge...the crystal goes up against the tapered cup and a plunger with a small padded tip is pushed (by the press) up into the center of the crystal to effectively shrink the outside diameter of the crystal by forcing the domed center up inside the cup. Install the crystal by placing the crystal into the crystal seat in the case and release the pressure on the press.
A 'crystal lift' is an expanding claw type tool that compresses the outer edge of the crystal...often leaving marks that may cause a leak on WR cases. They are cheap and good for removing a crystal that will be discarded or on a crystal that does not need to be water resistant for more than hand washing.            
Here are some of the different crystal types:
Here is an example of a cheapo crystal/case back press with tapered edge cups and plungers:
eBay item number  380890016220
Many vintage omegas use an acrylic crystal similar to the GS 'ET' type armored crystal. The problem is some omegas have a 'stepped' reflector ring/tension ring and it must be used in the replacement crystal or use an oem spec crystal.
Catch 22...many omegas have a 'mushroom' shaped acrylic armored crystal that presses into the case with the removable bezel already placed on the case (if it has a removable bezel).
'Removable' = the bezel can be removed with the crystal on the case but one of two things will usually happen:
1...The bezel will be bent from the pressure needed to remove it along with the crystal at the same time. It forces the crystal out of the case at the same time because the bezel will not come off over the 'mushroom' shaped crystal.
2...The crystal will be 'shaved' when the bezel ring is forced out basically ruining it and this can also allow the bezel to fall off later on. The bezel does not hold the crystal to the case...the crystal holds the bezel down on the case.
You see this type of construction on many vintage dress type omega 'seamasters' that have a one piece case with the movement coming out the front side.
How are you supposed to remove the crystal?
Use a Bergeon 5011 crystal pump or something similar that pressurizes the case through the case tube and pops the crystal out without damage to the crystal or movement. The crown comes out by pulling out on it to uncouple the two piece stem.
Note:  Sometimes the forked end of the stem will break and they are hard to find.



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