I dissolved the coating recently, but some Beral remained, so I pressed a 4" lap and slowly polished it away. I rechecked the figure and it now tested as a smooth asphere at 1/56 wave, which is about the same as the original sphere, which was equivalent to 1/20 wave.
The numbers mean little, but my plan is to mount it back in the original square wooden tube, and use it uncoated as a lunar scope. My star testing experience with uncoated mirrors showed me very beautiful lunar views.
Anyone familiar with building such a scope? Hints?