One-of-a-kind 1913 prototype Bullock Creeping Grip crawler tractor with its rare Heer opposed-piston engine gets cranking.

There are rare tractors, and then there are those that are truly unique, as in one of a kind. The Bullock Creeping Grip Tractor in the National Construction Equipment Museum’s collection qualifies.

Forget barn finds and car wrecks that have been sitting in the desert for decades. This twin-engine Allis Chalmers Model B tractor comes straight from old tractor heaven. Don, the owner, said this ...