Aequidens diadema. I think they are absolutely beautiful. Their coloration is subtle but elegant. Pictures don't really capture some of the coloration in the scales. I love the Acara over all shape.
I searched for one a while back. Looked around for about 3 months. Gave up for 6mo/a year or so. Then I happened upon one, about 5" long, at the one store I generally won't spend money at, but I was there with a friend. Brought it home. Had a nice 30g Qtank for him. Thought I had it covered completely, but sometime in the middle of the night he jumped on me. Found him about 8 feet away from the tank. It's been about 8 years (I'm pretty sure was when my oldest son was a baby), and I have yet to see another. I see metae and patricki's that are similar, but just not the same for me.
I've been on the hunt again for them for the last few months to no avail.