Okay -- you win, sort of, Ocelot. It looks to me like it could be used as either a ego to 510 or an ego to ego. But, since I have very few ego style connections.....I'll leave the minute details up to you.

(The second/er third picture makes it much clearer.)
I've used many a 510 to 510, and plenty of 510 to ego ones, (goes on the topper) but never ego to ego nor considered the need for one.
But, as I also have about every connector adapter ever made (we needed them in the olden times) I just might have to stalk the site to make sure I do have a complete set.
Edit: See --- Evil Zoe sees that, too.