I have an antique cast-iron furnace marked “INVINCIBLE FURNACE.” Based on historical research, I believe it is an Invincible Gate City soldering/melting furnace associated with Wm. A. Nicholas & Co. and the Invincible Manufacturing Co. of Wilmington, Illinois. Historical documentation connects the furnace to an August 11, 1891 patent and a 1897 Gate City Soldering Furnace and Brazing Torch advertisement. I have three I'm trying to establish how many examples are known to survive and determine the best way to sell it to a serious collector.
