I think 56 and 66 sights were only for flat side receivers, 57 & 48 were for round receivers.
According to the book "OLD GUNSIGHTS" by Nick Stroebel, the Lyman 56 application codes were:
56A- winchester 1892, 1894, 1886, Models 53, 55, 64, 65, 71, 1885, 87 Single Shot, Remingon Model 14 & 141.
56B- Winchester Model 1903, 63, 61, Marlin Models 1894, 36.
56BSA- BSA Model 12, Martini action rifles.
56C- Remington Models 14, 141, 25, Marlin Models 39, 39A, 1897, Savage Models 1903, 1914, 1929, Stevens Model 75.
56LA- Marlin 336.
56MB- Marlin Models 1893, 1894, 36.
56MC- Marlin Models 39, 39A, 1897.
56R12- Remingon Models 12, 121, 25, Savage Models 1903, 1914, 29, Stevens Model 75.
56S- Savage Model 99
56W- Marlin Model 1893.
56W71- Winchester Model 86 and 71.
