I can't rule out the possibility that they made both the zero and the 175 in the same year or at the same time, which is why the date range is conservative. We only have the 1915 Prisco and 1915 Rayo catalogs to go by, so far. Rayo was the house brand of the Standard Oil Co., who also may have had some influence on lantern numbering. I think it's most likely the zero model number (large fill) is confined to 1912-1914. Although Prisco closed in 1919, It appears they were done making lanterns by 1917. I'm still looking for evidence they were making canteens and mess kits during the war and never went back to lanterns after the war.