Aquila on them. They come in two sizes and two colours (brass and gunmetal). The 3 in the middle of the button is a little odd, but in both live roleplay contexts I can immediately think of (40k and of course, Maelstrom's Freiboden) it can be easily seen as part of regimental insignia of some sort.
Keep a weather eye on the blog, as this is the sort of button we design coats around.
What do you think of the buttons?