This yellow chip is offered as a premium with the purchase of a new book "Connected... Vegas Style", by Richard Wilk. It is advertised in Strictly Slots magazine and I believe in other magazines published by the same company.

There's an ad for Golden Nugget in the book and my guess is the ad was paid for, at least partially, with the promo chips. The book costs about $20 so it's not a bad deal whether you play the chip or add it to your collection. The ad contains the same picture of the "Two Toms" as is on the chip below.