Gruen Super Compressor 600 ft

I have a line on a Gruen Super Compressor 600 like the one pictured. I don't know much about the watch, but it is NOS and auto.

Anyone have any knowledge about these watches? I would be getting the watch for $500.

Thanks,

***Not the watch I'm buying, but same model. The one I am interested in is NOS with no blemishes***