...below are two Riviera 50¢ chips. The one on the left is N6249 in The Chip Rack & I have had it for a couple of years. The one on the right is from a reorder the Riviera made about two months ago. I don't really care about variations myself, but I will post them here in case they are not already in The Chip Rack, which does care about them.

As to your four questions, my answers are below. Andy - Las Vegas

1. Single listing.
2. No note is necessary.
3. I would NOT feel I was “missing” a chip from my collection.
3a. No