it is absolutely a platygyra brain, and actually looks like the boiling point platy that unique corals had for a lil while. i grabbed a piece three months ago, EXACT same pattern, but i won't lie, it started out about as vibrant as yours, but after a while in my tank, i won't say it stayed as bright. when i got it from vince at unique tho, it had very vibrant colors and looked great, as most of the LPS n SPS do over there. sad story bout it was, a golden eye chalice frag fell right on top of it (my tank is way too packed), kind of stung the platy while getting stung itself as well, and the chalice now is almost fully recovered.
the negative of that story is that i friggin keep the platy in my tank for almost A MONTH after it happens, see that some feeders come out at night, but not as long as they used to be, and not all over the brain as they used to be. the feeders start comin out less and less, but the flesh remained on the skeleton, lookin about 80-90% as colorful as when i got it. so i think hey, i guess no real problems. thing is, it wouldnt extend anythin anymore when i fed the tank.
now, i always seem to be touching, moving, and examining frags every time im by my tank, but this piece i dont pick up til recently, and what happens? the whole darn flesh "sheet" or "mat", for lack of a much much better term, starts falling off and disintegrating into my tank like a stung acan or RTNing acro would, and i was left with a nice hard brown skeleton with a few green dots (bits of flesh) where eyes used to be. the chalice that stung it basically formed a "hole" or "air pocket" for separation to occur between meat and bone. so, to say the least, i miss it greatly.
anyway, u have a SICC SICC piece right there, and in no way was i saying i had the same thing, i jus kno 99% that its a platygyra brain. cuz when i saw it in the store for the first time, i said to wifey "WOW that war coral got some funky lookin big eyes" and thought at very very first glance it was a favia or even echinata (i kno, echinata is weird, but really never saw a platy wit this distinct pattern and especially colors). best of luck with it, LET NOTHING STING IT (i thought platys win against other corals usually like echinatas do!!), and lemme get on a list for a frag.
that last part is a joke, i said it cuz its said so much to people who post IDs or pieces they jus got hahaha. and nothin against those people askin! i promise, i have done the very same thing. take care Oiseau Reefer, great lookin piece.
mark s.