Coryjoe - just as in Pennsylvania, there were many, diverse regional styles of longrifles being made in Virginia at any given time - throw into the mix the factor of different time periods and it gets even more diverse. You could hold up a fancy brass and silver mounted, wire inlayed Sheets rifle and a plain iron mounted gun with side by side and they could both be Virginia guns. You really have to break it down to a more focused look.
For a northen (lower) Shenandoah Valley style 1780-1790, the first thing that jumps out that that would be the first clue for something being from that region is the patchbox - but you have to be careful - the four petal edelweiss was also popular throughout the Valley and also shows up in Lancaster and York work too. You are right in that iron mounts would not be expected on a fancy Sheets rifle from that area in that timeframe- not impossible, but not typical. But they would be appropriate for a 1790s gun from Botetourt County Virginia, which is maybe 150 miles southwest, or farther south and west to places like Wythe County or over farther near Tennessee. Iron mounts were often found on guns made in Southwestern Virginia at least by the 1790s, on guns both severly plain and some relatively fancy - and many of these smiths worked in iron and brass. So these are also Virginia styles.
I like Ed's decision to use a York influenced carving style. Shows the proximity to multiple nearby influences and I love those sort of guns. There is a Phillip Sheets attributed rifle with a large round faced lock, looks pretty early as far as that group of guns goes, with a Lancaster daisy style patchbox in one of Whisker's books. Gotta remember that York County Pa. was much bigger at the time - included what is now Adams, etc. and that lower Shenandoah Valley/ Maryland/ Shepherdstown/ Pennsylvania border region was a real crossroads of regional styles due to the travel of gunsmiths, hunters, settlers, soldiers and their rifles up and down the Great Wagon Road.
I love that big Chambers round faced lock - but for an early Golden Age valley gun or southwestern Virginia gun I wish someone was making a production 1780s-1790s English export lock - something akin to the lock on the Conrad Humble rifle. Jack Brooks has a great set of 1790 Ketland castings, but that's more than I want to tackle for a build, at least at this point.
Nice rifle Ed.
Guy