Dennison cased Seamaster crystal replacement

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My newly acquired Seamaster has a Denisteel case with number 4322 inside the caseback. I assume this a model reference number, but I haven’t seen another with this number. It has a cal. 420 movement with serial 16 2xx xxx which dates it to circa 1958.

I would like to change the crystal because the original is cracked and grazed. Currently, it is an acrylic crystal with a gold tension ring. It doesn’t have the omega logo etched. The dimensions of the crystal are 29.6 mm x 4.7 mm. Do these Dennison cased Seamasters use Omega crystals (if so, would someone have a part number)? Otherwise, I’ll probably go with a generic crystal (e.g. from Cousins).

While we are discussing the crystal, the case is in three sections (caseback, middle and bezel). I am wondering about the order of reassembly. Should I install the bezel on the case before installing the crystal?