emil flues created the design for the ithaca flues gun around 1906, when smokeless powder was still relatively new and generated pressures similar to black powder...one of the results of ww1 was the development of so called improved smokeless powders, which created significantly higher pressures than did the older smokeless compounds...the original flues guns were not designed to handle high pressure loads...as a result, ithaca did beef up the flues receiver and add an extra screw to the forend around 1918...flues model guns were then phased out of production in 1925...and replaced by the new ithaca double, aka nid...which is an even stronger gun than the late flues...
