Although I don't have the name, a recent theory is that they are the initials of a gaming operator within Harolds. It was not uncommon, especially in the early days, for establishments to have a separate individual(s) run the games while the owner ran the rest of the business. The owner got a cut of course. In some cases, the chips had no reference to the current venue while other times they did.

This makes more sense to me than a cancellation mark that you have to hunt for. I have the chip as well. Beautiful chip.

Pete