WOW, that's a heck of a first there!! Have you done any research on that bad boy yet? It doesn't sound like you know just how amazing that find is.
Edit: Okay, here's the info for you. Sorry if you already knew this, but at least I can share it with your viewers at home. You really knocked it out of the park with this one. There are a number of fakes of this button, so please post back pictures. That said, you're in the right area to have found the real deal, so unless it was found on the town commons where a reenactor might be, I doubt it's fake. Anyways, on to the good stuff:
B0821 Texas button, Texas Cavalry, low convex one part cast brass, southern wartime manufacture by T. Miller, blank back, (20mm)
Button depicts bold "C" on lined background with wide border, low convex cast bass button. This is Confederate wartime manufacture for Texas cavalry. Backmark: blank back, cast button with deep concave well, shank was integral cast, then drilled, manufactured by T Miller, Houston Texas, (BlankSouthern161). One part cast button, low convex, back is concave, casting is crude southern "local", coat size. Dug button, shank intact, deep concave well around shank. Recovered: Gulf Coast defensive camps near Houston Texas by Cody Hudgeons.
Ref: Albert CS143, Tice CSC280A2.
http://relicman.com/buttons/zArchiveButton2Texas.htm
I was trying to find a few exaples of this VERY rare button for sale to give you an idea of what they're selling for. But they're so rare I could only find one. Here it is, scroll allllll the way down, and I'm pretty sure you're going to like what you see:
http://www.historicalshop.com/sitecontents/confederate/artifacts.htm