I used this as a chair in my room as a kid in the 60's, and it was old then. I think I recall it was from a truck, maybe a Stewart, circa 1927? (I could be wrong, my memory is fuzzy, but I found a '27 Stewart speedometer...) The base measures aprox. 18" wide, the bolt spacing for the rear mount is 13", distance from the front mount bracket to the rear bolts is also 13".