Hi Jon,
I think a high end British fowler from that period with out a standing breech (hook and tang) and with pins holding the barrel would be pretty rare. Military, trade, and livery guns, yes but not first class sporting guns. Standing breeches are not hard to inlet, just solder or glue the tang on to the hook in the barrel and inlet the whole thing like you do a barrel tang. I understand there is a supply problem buying them right now, however, The Rifle Shoppe has several kinds that are correct with the proper bottom lug for the cross pin and they seem to have worked out their shipping issues. All of my last 3 orders, including complete parts for a pattern 1730 Brown Bess, arrived within 3 weeks of my phoned-in order. I got a batch of hook tangs within 7 days.
If you are going to use the plain plug and tang then there really is no reason to use barrel keys. The whole purpose of the keys and standing breech was easy barrel removal for cleaning. With respect to inlet barrel bands, I used those on an English fowler because I simulated (as best I could) a Spanish barrel. Italian and Spanish smooth bored barrels were considered the best in the world and London gunsmiths sometimes were reluctant to braze on barrel lugs because they were afraid the heat would destroy the shooting qualities of the thin walled barrels. I've only seen those bands used on English guns with Spanish or Italian barrels and sometimes Turkish and Indonesian Damascus barrels. Sometimes the bands were silver along with the mounts. I would probably solder lugs on the bottom with your barrel.
dave
