It was indeed a Dealer Accessory, for 47-53 Chevrolet Medium Duty trucks. There was a smaller version available for the light duty trucks. I've owned three of them. I sold the one I had on my 53 Chevy COE Wrecker, to someone on here, several years ago.
Spanky Hardy Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers
