The first model six lamps had insulated burners with no dates. After the prize was won, the date was hurried into production by stamping the date on the wick adjuster knob.
Later the wick adjuster stamp mold was modified to include the date. Then starting 1917 through 1920 undated uninsulated model 6 burners were built for the Canadian market. Aladdin applied for a patent on this burner on 28 Aug 1914. The patent was filed on 19 Feb, 1918 after sales of the model 6 had ceased (patent 1256879).I do my very best to give as accurate descriptions as possible. I strongly urge all buyers to examine the photos and read the description carefully. Please use pictures as part of description. I do not claim to be an expert in any field, and determine quality and condition based on judgment. I check my page often and will respond promptly.