Here is a 120V Fisher Pierce photocontrol. The cover looks burned on the right side of the window. I would like to open this up to see what it looks like inside but I don't want to crack the cover.
I have one like this too. Joe had said that it was because these were used in a post top with the decorative cuploa cover and the cover wasn't perfectly aligned with the window. Yeah these are brittle. I've opened some up to fix them and get them working and I end up needing to superglue the covers back on.