Thank you for the replies. I'll have to keep looking. There are a few bubbles inside the glass toward the bottom. One small, and two tiny ones. From what I read, uneven bubbles can be a sign of blown glass, vs even distribution is more likely pressed. For what thats worth...
Background reading here is around 40-60 CPM. I should just leave my meter on all day while at work to get a better reading. I've only sampled background for a few minutes at a time.