Recently acquired a 6.8 AR with the barrel stamped M1S 6.8 SPC. Removed the flash suppressor and found it was threaded 1/36. Not sure of the AR's history other than it is at least several years old and was in like new condition. 1/36 barrel threads are uncommon but they do exist. A few companies online sell flash suppressors with 1/36. My questions is: Are 1/36 threads possibly an indication of when the barrel was produced. Maybe in the early days of the 6.8's introduction? I plan to call M1S and ask. Thought I'd float the question here first.