Bone, pinner's bone

Pinner's bone. Bovine metatarsal, left side, fused. The lateral and medial sides at the distal end have been sawn off. The centre condyles have gone entirely. There are four facets at the proximal end of the shaft with seven grooves cut into the longitudinal axis by a saw. There is a longitudinal crack running from the proximal end on the the medial side along the shaft of the bone. The foramen is very small, and the proximal end of the bone has been enlarged. The bone is almost entirely covered with copper salt staining. There are file marks on every side.