That style shows up a lot in many Ohio rifles and can be seen in many photos found in the Ohio Longrifle Association's books. My buddy (and I would guess others) refer to this as the "National Road" style of patchbox. They were used on both fullstock and halfstock rifles.
The theory goes that this sort of patchbox was used by smith's that lived withing a certain milage of old Route 40 (the National Road) that ran from Washington thru Pennsylvania, into Ohio and onto the west. Depending upon who you speak with it could be anywhere from 20 miles to 40 miles, could even be more, could be less. There is also the belief that certain manufacturs from the east provided their brand or style of castings, guards, inlays, sheet stock patchboxes, capboxes, barrels, triggers, locks so forth and so on in dedicated territorries and these goods were sold via traveling salesmen or hardware stores.
I gleened this from table talk, rubbing elbows with collectors and asking questions.
Hope this helps.....
