Hello, All. One of the guys at work brought this in. He bought it from a 90 year old gentleman who told him it may have something to do with trolley cars? Overall length is 10-1/4", and the female drive opening is 5/8". The handle is a square tube, the head pivots in a yoke style fitting, tension is adjusted with the nut and bolt that pass through the tube to the yoke. Only marking is PAT PEND' . There is also a flat spring within the drive opening. Thanks, Lou