I've got one... 'course it's not nos, but looks like a decent used one. I might ask for your help, deuce lover, to make sure I've identified it correctly.
there are only a couple of things that can go wrong. Cracked solder joints and dirt. I have found insect nest in the vent lines and they usually blow out with compressed air. Cracked solder joints can be resoldered after removing the old solder and cleaning.