That was my guess. Or a lituus. I get those confused, and they seem to have similar shapes, especially when they are stylized on coins.
According to the literature it is a lituus, though simpulum is a very good answer. Thanks to all for playing my little game.
That's what I was talking about in my first post. I guess I wasn't clear. A- rather than an A for me.
Nicely done! I had that coin bookmarked for a rainy day purchase, but I'm glad it went to someone who knows what it is.