Found two large twist drills in a lot of other stuff. The one above was too badly corroded from obvious neglect and was beyond redemption.
Out of curiousity, I cleaned off the shank:
BSA Tools. Now if that isn't ironic. Seems the drill bit suffered the same fate as the parent company!
Perhaps more ironic still was the fact that the other bit had better withstood the same neglect and remained in much better condition:
It was made by Steyr of Austria, better known for its firearms. Unlike Birmingham Small Arms, it's still in business today.