Interior Tension Style. #1 size (2-1/2" slip chimney). One piece burner. Patent date Feb 1, 1870 is mistake, it may refer to patent #99,289 for a manual extinguisher which is not present. Burner conforms to patent #75,566 by G. Neilson. The patent is for springs to hold chimney on the inside. Sept. 16, 1862 patent is for the wick tube design.