Buck ball, tent grommet, and unkown

I got out on a new spot for the season today. I found a button back last week, so I knew I had to go back. I'm happy with today's finds. It's enough for around here for sure!

Anyone have an idea on the copper piece? At first I thought it was a blown out shell casing, but if you look close, there are slits all the way around the big end and it is made with lots of "fingers" like it would fit over something. It was within 6inches of the grommet.