[This is my very first post - I hope I've got the protocol right!] Got myself a 41. I just love the fat tank! I suppose some of words we may use to describe the tank are bulbous, podgy, portly, stubby or tubby. It great when you get a 41 with the brass fuel tank that isn’t dented in any place. This is the roaring version. The letter code seems to read “AV 3 Z” but I can’t be sure. Many of these stoves seem to be lightly stamped or even half stamped. The area where the code is was polished by the previous owner presumably to get at the code. Unfortunately, it is missing the push-knob of the pump. It does not build up pressure and needs a new cup which I have - just haven’t got around to fixing it. It should clean up well but I haven’t the time. It looks like the original paint was Drab Olive. As you all know well, the inside top lid has a fold-out, hinged flat steel windshield that hooks into the pot support frame when deployed. The stove just feels solid and well made.