I am a 1998 graduate of The Citadel. The grey chevrons you have above look exactly like upside-down cadet corporal chevrons from the 1870-1900 period of the Citadel or possibly the same period for another military school (VMI, West Point, etc.). They might be postwar. But I had a pair when I was a cadet corporal at Citadel on the forearm of my dress blouse that pointed upward. Those look suspiciously like they are postwar, though. I can tell they are old though.
The modern picture of Citadel cadets is a picture of current school president Gen. Rosa. The one on the far left is a cadet sergeant (two stripes facing upward on the upper arm) and not a corporal. I was a cadet sergeant as well.
Not saying that they might be period militia, but I think they look just the like chevrons I once wore on my uniform. Same texture of material and color that go on the dress blouse (no tails, but a high collar), not the full dress blouse (the one with tails to it).
I'd post a picture, but I don't know how.
Check this link for more of what I speak. There is a historical section to it with pics if you can find it.
Thanks- Johnny Lloyd