Patent dates on lanterns were actually a very casual and random thing. Patents often had nothing to do with the lanterns they appeared upon, but were more a form of advertizing. Dietz made regular random changes to patent sets to mark production runs. Many of the dates seen displayed on lanterns are bogus and not patent dates at all. In this case the 1891 date is a Sunday and the 1898 date is a Monday; therefore, they never were patents. Dietz was the only maker that was consistent in using real patent dates on lanterns, but not on globes. The 2-18-18 date, on Dietz short and little short globes, is bogus. Likewise the January patent on the Junior Loc-Nob is also not a Tuesday and not a patent. As if things were not mysterious enough! BB