...is that I'm really guessing! Probably paint.

Scan 1. Here's my puppies with the some prime examples of what has Jim bothered by these inserts. The grey $5 is the sloppiest set of inserts while the orange $100 has the most uniform inserts. All edges square and actual table wear evident though minimal.

Scan 2. This shows the commonly seen hourglass figure insert on the orange w/black $100 that Jim was talking about while the brown w/yellow goes hourglass as well as haphazard. The grey looks like a Splashbar project once again. I've included a high quality modern chip for comparison (A-crest) as well as a low quality modern (Paul-Son).

Scan 3. Some interesting artifacts here. The orange has a contrasting fleck in the black insert but I've seen that in manufactured inserts, could be an extraneous piece of colored clay. The brown at right has what may be a brush hair stroke in the upper diamond itself but ... who knows? The brown at left next to the numeral shows two different rim knicks that are worth examining. The knick nearest the numeral has coloring down into the knick itself, something I see on the other Nevada Club diamonds while the 3. knick lower near the edge of the insert shows what may be contrasting clay color from underneath. I don't have any clearcut examples of rim knicks, scrapes or scratches exposing color otherwise.

I haven't dug through my collection to check other Diamond mold inserts yet either but I'm not seeing such inserts on the Langworthy, Burts, Christy & Jones or TR Kings I have at hand.

Let's consider the source now. Lincoln Fitzgerald was the owner of the Nevada Clubs in Reno and Tahoe. He certainly had his ecentricities and his only Nevada confidant that I've ever heard of was his wife Meta. It would be easy for me to believe that if he took it into his mind to paint inserts on his chips for his own unknown reasons, it would happen. The men would be in the Men's breakroom a'painting and the ladies would be in their lounge doing the same. Fitzgerald would be doing the thinking thank you, reagrdless of what the chip supplier could offer!

My best guess.