They seem to have been used throughout much of the southern Appalachian areas where mountain rifles were made. I have seen them on rifles from North Carolina, Southwestern (and parts of what is now West) Virginia, as well as various places in the Tennessee mountains. The pointed tang as well, in varying lengths.
Some of the other styles (like those sort of "heart" or "spade" shaped finials shown in Dennis Glazener's Gillespie book) seem to be a little more region/ maker specific.
The long tangs coming up over the comb seem to turn up on Tennessee and North Carolina mountain rifles by many makers. They may turn up on some Virginia guns too (?) but I personally do not know of any. Usually the pointed tang seems to be the most common on the SW Viriginia iron mounted guns.
Guy