Opened up the Gruen precision watch and it’s a 510RssCA stamp on the inside of the case back, but the movement is covered. I have no idea how to remove it.
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Could it be a press fit cap? I would use a soft implement to lift up at any seam, and if that isn’t available my next step would be to attempt to unscrew.
Think that is an anti magnetic feature, not sure that is what they look like on some Vostoks I service, it just falls out but on Russian made watches a lot of components just fall out.
I'd assume it's snaps off with a case knife but as @GotTheTime alludes, eyeballing to find a little groove for lifting (they can be hard to see) at the edge would confirm this. But I'd also just turn this all upside down and give a few light taps to see if it comes loose.
@GotTheTime @MatthewT @PoorMansRolex was able to use tweezers to pull up case by the crown. Thanks guys!!!
Not to sure brother good luck 🍀