Twenty or thirty of the micro-drills in the Greg Perino

collection were polished from end-to-end. They were

not smoothed by drilling but were eaten by birds,
either chickens or turkeys. The polishing effect was

caused by the grinding process in the birds gullets.

The micro-drills in this picture range in size from
9/16 inch (1.4cm) to 13/16 inch (2.1cm) long.