[Bob Bidonde]

Cape Coder,
The brass distributor on the rotor is rounded with a curvature compatible with the inside diameter of the distributor body.
Kurt In New Jersey,
I think the 0.025" gap is an opinion of Model A experts. I however, use 0.015" because the smaller the rotor gap is, the lower the impedances to the spark plugs are, so the sparks have more intensity.