I think that the old 12mm. French walking stick gun cartridge had a great deal of influence on its development.

PeteM, that tranformation was worth the effort. I quite like the little .410, I have a double hammer by Stensby of Manchester, a single .410 converted from a rook rifle by Ebrall of Shropshire, a Belgian double, an AyA boxlock ejector and a really interesting one that is a double hammer gun with one barrel .410 and one barrel in .300 Rook rifle by Rosson of Derby. Lagopus.....