The end of a pickled onion fork. Used to get them out of the jar if it had a handle.

Lets Go

black, poorly crystallized diamond

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If that picture shows the bullet seated in the case then it will never chamber properly in an existing rifle. The factory loaded round that is shown for comparison will be very close to the rifling of the barrel when chambered so the experimental bullet will a) not fit in the magazine and b) will be forced up the barrel (or back into the case) when the bolt is closed.

If the grooves are not screw grooves but individual circles it could be a bore guage to measure the internal diameter of a tube.