Just about every American starfort defending any sort of waterway got a hotshot furnace or two in the 1840's, and a standard kit to build them was manufactured for the US Army...need a hotshot furnace? Send away for the kit! This resulted in a level of standardization that certainly wasn't present for the construction of the forts thelselves, and these furnaces had a very distinctive shape and style...and they most definitely did not have these angled supports on both sides! It's an awful shame that neither of these furnaces survived, because I'm having a hard time visualizing what they might have looked like.