I agreewith Guy that time frames and regions sometimes get compiled into lump sum statements. Very easy to converse on known and accepted traits of 19th century guns only to find the context is really about pre. rev. Then in a week on another forum, those traits are being accepted as dogmatic facts on much older guns. In reality all one has for these older guns is speculation. Last time I checked it is hard enough to find any American made gun with solid provenance to those early dates.
In my mind, it is best to go with the preponderance of the evidence in situations where you have known like later southron pieces.
Here are a couple of early quotes for iron guns. Where they were made is unknown but the 1776 quote would give me cause to set a loose historical foundation for a Virginia made fantasy piece.
The South-Carolina GAZETTE
June 12, 1755
CHARLES-TOWN
Berkley, County, Seluda ff.
.... where being known and challenged, David Dundass, instantly made his escape, leaving a smooth bor'd gun, iron mountings, and well fix'd, near four feet in the barrel.
THE VIRGINIA GAZETTE 3
January 12, 1776
WILLIAMSBURG
ON the 6th of this instant was stolen, from a soldier of my company, a RIFLE GUN , her stock made of persimmon tree, iron mounted, has a pistol lock, the box lid lost, and her bore very small.