https://imgur.com/a/ZoL1C5n

There's an anti-glare/implosion plate adhered to the front of the CRT. The glue that bonded them together rotted with age.

I heated the whole CRT to 75C using a heated chamber 3D printer to soften the glue. With a bit of convincing the plate detached. After cleaning the remaining glue, I reattached the plate with some 3M VHB around the edges before sealing out the dust with gaff tape.