A different type of "milsurp".

Wife and I just got back from a trip to all the remote Upper peninsula of Michigan outports. One of the places we visited was Copper Harbor at the far end of the Keweenaw peninsula, an area known for its bitter winters. Wood burning stoves are de rigeur in the area and while we were checking out some of the local stores we saw an old WWII U.S. Army Cannon Heater #20 in one. I talked to the proprietor about it and she told me she swapped some surplus antiques for it back in the 1980's and that it keeps her entire store toasty warm in the Winter. You can read more about these versatile heaters here:

US Army Cannon Heater No. 20: Understanding Its Value and Importance - News Military

I put a lot of coal through one of those. They were still in use when I joined the Army in 1968 and a couple decades after. They were ubiquitous in the orderly and supply rooms of the old wooden WW2 barracks still prevalent on countless Army posts. On Fort Knox, they were also used in the "warm up" shacks on tank and rifle ranges. During the seventies and eighties civilians were stealing them faster than Range Control could replace them.

Looks like something I'd add to my bizarre collection. Have to find the right yard sale.