For TRK chips, I have only seen them on this Nevada Clubs high denom. My guess as it was a way to track the high denom chips, but don't have any proof.

The only other chips I can recall that have serial numbers are on the HHL mold from Diamond Jim's Nevada Club. I think they stamped $1, $5 and $25s. There are probably others, but these are what I remember as of now.

Very nice small crown set!