In the U.S. most makers "got by" with a couple of frame sizes, L.C. Smith, Fox, Winchester Model 21, etc. Then there was the Brothers P. with so many frame sizes -- 7, 6, 5, 4, 3, 2, 1 1/2, 1, 1/2, 0, 00 and 000. Parker Bros. made 12-gauges on 1-, 1 1/2-, 2-, 3- and 6-frames and in late years the 1/2-frame that I've seen. I've seen their 16-gauges on 0-, 1-, 2- and 3-frames and 20-gauges on 0-, 1- and 2-frames.