Climate Controlled Sfba, CA
I bought a PotO many years ago and having the screen on the outside of the glass didn't feel right to me so I covered it with a very thin piece of plastic before I put it on route. Because of this, my glass mask art is intact. My playfield had two serious burn marks in the flasher inserts but back then, I located a NOS playfield so I'm set up for my restoration later. 
Steve
Quoted from Blipsqueak:To answer a few posts here, there is paint on the front and back of the backglass. The mask is on the front and is typically gone if the machine was ever public. It's a pretty awesome effect when the lights behind shine through to show the face. I've seen a few in person and only one or two have had the mask intact. Oh, the one I bought from corvair61 is in great shape (aside from the missing gold and outlane wear)
