That's an Explore Scientific, Nitrogen Purged (no fogging), 82* AFoV eyepiece.
Waaaaay to much power for my Mak.
Super in my f6 refractor and f5 Dob though.
One of a pair I bought for binoviewing with my 815D, but turned out to be too much at that FL.
Very close to a Nagler and 1/2 the price or less.
New and unopened.
$100 inc. express post.
PENDING to Liz.