spg console gauge gauges depth pressure compass

I have two black face and one white face 3500 psi Scubapro spg's with bezels that look like they can be unscrewed. Have any of you taken these apart? Aside from the spool, I'm guessing there's an o-ring between the glass and body that should be replaced. I'm pretty sure the black faced ones...

Looking to pick up 1 or possibly 2 SPG. Must be in Imperial units. Figured a couple people may have some that they'd want to unload.

hello all I'm new to diving and currently in advanced open water class, my check out dives are in a few weeks and I am interested in buying a cheap 2 or 3 gauge console as a back up to my Galileo Luna. Depth, pressure and compass if possible would be great. Let me know what you guys have.