Based on the condition of the paint I would think it is original. It has a blue line on one side which I am guessing that it either had a sprocket on the white only half at one point or it was on a kart where only one side mattered. 5”? Also you will notice that there is a little more material on about a third just outside where the bearing sits. Made me think of a wheel weight but its part of the rim. Odd that its only on one area of each half. Thoughts?