In 1810 France used two systems. One similar to the British system but based on a different pound, to determine gauge and a bore system based on the kilogram. The bore system was abandoned in 1868. Some time later, the English proof house decided that guns smaller than 10.6 mm (approximately .410") would be tested differently from larger ones. Pietro Fiocchi deemed that the .410, officially 12 mm in France, became the divider between serious guns and play guns.
In the 1870s a Wilkes .410 was proved by London Proof House. During much of the 19th century various English authorities declared the .410 unfit for serious game shooting.
In 1914, CIP standardized 12, 14, 16, 20, 24, and 28 gauges. In the 20s and 30s, 14 gauge disappeared and 32 reappeared. Sometime in the 20s, perhaps spearheaded by a German or Swiss wanting a logical progression CIP used the 36 designation. Later CIP reverted to using the correct .410 designation. In 1961 CIP made .410 the official designation. In 1969 CIP added 36 in parentheses. For many years, manufacturers in Italy and other countries labeled 2" and 2 ½" .410s 36 gauge and 3" .410s 36 magnum. Thus hundreds of arms and ammunition manufacturers have historic and other reasons such as marketing and sales for using two or all three designations.
In the USA, the 44 shot aka 44XL based on 44-40 brass was very common. The .410 was first chambered by Stevens as a single shot in 1915. In the early 1920's Parker produced a .410 sxs.
Pete
