Dig, As Ben said, it should come out with the panel. I looked at the one on my '50, which is still removed from the firewall, and see no evidence of gluing on mine. If you don't have it out already, I think you'll find it not to be a problem.
Assuming that you're removing the speedometer for repair, and if you haven't already decided where to send it, I was satisfied with the speedometer repair and price for my '53 from Instrument Services, Inc. in Machesney Park, Il. 800/558-2674 for what it's worth.