How rare is this? Superheat Safety Switch Package Unit pt# 5910397 for 1958 Chevrolet Cool Pack. Still in the box complete with instructions.

DD

Sounds pretty rare to me, altho I'm far from being an expert on Cool Packs.

If I owned a 1958 with a Cool Pack I would want it for a spare. Problem is there probably only a hand full of '58's with Cool Packs remaining.
I would assume that the switch cut out the compressor if its low on Freon, thus avoiding destroying the compressor.