Notched chips are production samples that came from the manufacture, casino or were salesman samples.

The manufacture kept approved notched chips for re-orders. The clients were sent notched chips for production approval. Salesmen would present notched chips to prospective clients - didn't hurt if you could show that prominent Vegas casinos were using your chips.

The absolute best are notched chips that were rejected for some reason - chip color off, wrong inserts or inlay printing was incorrect.

To each his own, right?

Below are a few of the ones I've picked up. A couple are notched and drilled!
Hard to tell from this scan but each of the three Sahara 50¢ chips are a bit different.
Many of the Panama chips were never put into production.

Pete