I was just given a 5x7 Brumberger contact printer.

Inside there are three incandescent lamp sockets and a sheet of (flashed?) opal glass.

I looked online and found a picture of one with a frosted lamp, a clear lamp, and a red lamp.

The red lamp I understand...to get things set up, adjusting the easel blades etc.

Was there some purpose to using a clear vs a frosted lamp, considering it has an opal diffuser? Or maybe the clear lamp happened to be smaller, for different exposure times? It doesn't appear to have a switch to chose which lamp lights...it looks like it has one momentary switch to turn it on with pressure on top.