I have a habit of sweeping the ground with my foot to remove leaves and debris while digging bottles in old dump sites. I was doing just that to sweep glass and leaves aside and a piece went right through my boot and deep into my foot. I won't be doing that anymore. Stay safe!
Spot back here where I found about two dozen of them. All were screw tops of different sizes. I kept one of each but they appear to be common as I've seen them in a couple other spots too. I do admit the blue color is nice.