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A strange blue coloured belgian rock was it? I've heard of them yeah. They're quite dangerous. Best send it to me to dispose of safely.

Maybe you're supposed to use it to crack a beer open when you're done?

:rofl2:

Or perhaps its a thing for taking stones out of horses hooves? :D

The barbers notch appears to have the hollowed out shape to allow a fingertip to be placed in it. I'm gonna plump with 'to help open it'. :o