Look at the selection of Small Crown chips below. Some of the edges between colors are straight and some are crooked. One even looks like an hourglass! I think it depended on the process at the plant the day the chips were made. Differences in temperature, consistency of the clay, skill of the person laying in the inserts, and the pressure on the press.

I know, when I started collecting, I thought the "sloppy insert" chips must be painted too... but (with a few exceptions) they are just the way the chip-maker did them. As I recall, Sharkey did paint inserts on some chips to save money?, and not the chip I show. There were also some roulettes used in Puerto Rico that had hand-painted edge spots to replace a missing color (so I was told by AlbertR).