Looking at the 21st US Infantry,
The US didn't use chevrons until the 1830s
Yes, you are correct about rank chevrons but the commanding officers of regiments were given a certain amount of license on how to organize and dress their units during the War of 1812. The 21st was one of the few units in the army to organize a grenadier company. They were distinguished from center companies by two chevrons on the upper right sleeve, red tipped pom poms on their shakos, and the practice of tucking their overalls into knee-length gaiters. I had to put chevrons on both sleeves because that is the way the texture sheet is set up. Many regiments also had light companies as well but their was no official regulations on how they were to be identified. It was up the commanding officer. In the case of the 21st the decision to form a grenadier company was made by their former colonel and now brigade commander, Eleazer Ripley, after the 21st's light company were disbanded when they disgraced themselves in a riot. This is all contained in the book, Osprey Men at Arms #345, "The United States Army 1812-1815", which is usually a pretty reliable source.
