This one is really unique. It's a c1972 Hughes Aircraft Company model 3157H argon ion laser head that was built for airborne use. And "built" it is! The thick metal outer cylinder serves as an "exoresonator" that includes the end caps which hold the mirrors. Water cooling connectors are seen at the rear, and pass through the outer cylinder to an inner cylinder.
The plasma tube extends out the front (output) end of an endplate, which includes three pass-through connections and what looks like a gas fill connector. The endplate is held in place with a huge snap ring I didn't want to remove. The rear Brewster window and extension is held on by a vacuum flange. All but two screws on this were missing so I assume it has been removed in the past. The tube is not under vacuum.
The head is 25 inches long and weighs 26 pounds. There's a Navy sticker on it, and the serial number is M3005. I was told it these were originally part of an Air Force contract starting back around 1965, right after the argon ion laser was invented at Hughes.