Really Nice! I once saw a NGC attributed CUD on a Cent and the piece of the Obverse Die that had broken off.. They put them in 2 slabs
I didn't see your coin on http://cuds-on-coins.com/. I'm sure they'd love to get some pictures and add it.
I got a '21 Peace Dollar I found on eBay on the site as a retained cud. Not even mentioned or noticed in the auction.