That is a DG2813 chinese movement.
Poke that button and the crown/stem will release, then the movement will come out - it’s held in place by the plastic ring.
You’ll probably have to reposition the overlay.
You have to remove the hands and dial to access the date wheel, carefully remove the overlay with a x-acto knife and reapply it in the correct position with dial dots.
This is a low beat movement, is it the same as the original poster?
I'm wondering is this movement can be stripped and rebuilt or will it explode when I take the back plate off?
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