You have presented some evidence that Oerter's work was known somewhat further abroad than one might think.
My honest opinion is that his rifles
weren't widely known at all at the time. The Baer/Oerter rifle is the only one of his rifles that we know was purchased by somebody "far away" from Christiansbrunn--and the Baers may have been family friends.
Andreas Albrecht supplied eight rifles with "brass boxes" in summer 1776 for Colonel Miles's and Atlee's provincial regiments. Men in these regiments came from a wide range of places and the regiments marched through New Jersey and New York. Maybe some of the men who carried them scribbled their names on the brass boxes. Imagine if some of those eight rifles survived, today, and we could trace who possessed them during the war. Perhaps one man was from Northumberland County, another from Cumberland County--a third from Bergen County, New Jersey, and a fourth from Long Island. Knowing only this, we would probably be amazed at how widely Andreas Albrecht's name as a gunmaker was known! But in actuality Albrecht was known in none of these places.
It is likely that Coykendall and Hankinson acquired their rifles in the same way. They probably didn't order up an Oerter rifle from Christiansbrunn--at least there's no reason to think they did.
The Baer/Oerter rifle ought to be a
cautionary tale for the sort of story we have told about these rifles that inflates Oerter's reputation at the time. The Baer/Oerter rifle circulated through
many other hands than Baer's--none of whom knew Oerter whatsoever. It is unusual to be able to trace an eighteenth-century rifle to a particular owner, but knowing who possessed a rifle at some point in its life and knowing who purchased it from the maker and for what reason is an entirely different matter.
Rifles, including (we now know) very high-end rifles, circulated widely in these very years we're discussing (the 1770s). In Pennsylvania thousands of rifles were taken from their original owners and put in others' hands. It's like the bouncing ball on the roulette table: round and round it goes, where it stops, nobody knows. I wouldn't rely too much on where a rifle happens to have stopped.