In fact, some of the Odyssey data makes no sense at all.
You all have Shooting Gallery and the Shooting Gallery Gun as two separate listings. The game you rate as R9 while the gun is rated as R6. However, neither item was ever sold independently of the other. Shooting Gallery, when it's complete, comes with the light rifle, eight screen overlays, and game cards 9 and 10.
The four games that are played with these two cards, overlays, the rifle, and instructions are Prehistoric Safari, Shootout, Dogfight, and Shooting Gallery.
Shooting Gallery is just one of the four games in the package. It's not a game on its own. Therefore, you can't have them listed separately, it makes no sense. The whole package is often referred to as just Shooting Gallery because that's what it says on the box, but the rifle comes in the box! To quote AVGN, "What were they thinking?!?"
As to the rarity, R6 is about right. There aren't too many, but there's always one or two on eBay.