Jay, I'm sure you know when those chips were ordered, I don't.
But it's turning out to be a little confusing.
Chips ordered for a place that was closed a few years earlier.
We know the Plaza was there in 1955:

http://digital.library.unlv.edu/objects/sky/1784

The "Palace" opened there in '56.
They closed in '59 when Harrah's took over that property.
Why those chips were ordered in 1959 is a mystery.