Are the ribeye caps you speak of, sold separately at Costco? My wife just eats the eye so I get a cap for my next day’s lunch.
Yep. That fatty, amazing outside strip. Possibly the best piece of the cow. They pinwheel them and tie them into steaks. I recommend uncoiling them and putting the strips on skewers, and a minute on a wicked hot grill. God it's good.
Oh, and your wife is crazy! But you're the beneficiary! 
Ribeye caps are among the most underrated cut on the cow without question. Also a big fan of the picanha--the top sirloin cap.
Those are called the coulotte steak.. I was in the meat industry for 35 years and we were selling "coulotte steaks" back in the '70's. We cut all the steaks for the Keg & Butcher Baker Candlestick Maker Restaurants and they wanted center cut only. I bought 20,000 pounds of whole choice top sirloin a week. So, we had all the caps left over and marketed them as coulotte steaks. Pretty good steaks...they plump when you cook them.
And yes, Prime Rib is a cut...not a USDA grade. There are or used to be quite a few grades...Standard ( mostly dairy cows that were boned and ground for burger-- USDA Good -- No roll, a non- grade . the packers would have the federal meat inspector not roll the beef with a grade stamp--it was not quite marbled enough for a choice but better than a Good. That way they got more money for a "no Roll" than to roll it with the Good grade.-- USDA Choice -- and USDA Prime. I would put a Prime grade NY strip on the shelf in the cooler and leave it for 45 days before cutting it. Can't describe how fantastic that was..I was really spoiled.
