Nice 2 face. I had 3 simese twin nem babies I found in my tank that slowly merged into one head 2 were true 2 faces but disapeared early on and on the other both heads were the same color but it eventualy disapeared too. The 2 bodies with separate genetic codes merged together is known as chimerism it happens when one twin absorbs another so completly that sometimes the individual's organs or body parts will have diffrent genetics all in one body.
3 of mine had various stages of division of the heads the one that lived longest was 2 complete separate heads that eventualy developed into one disk I imagine this also happens in the embryonic stage and they come out with an alredy merged bicolored disk. Sometimes the tentacles even will have difrent textures or lengths or the disk will have a totaly difrent pattern not just color streakes or patches. Streaks or blotches show up on some nems. The streaked ones are usualy called painted rock flowers but some sellers try to pawn them off as 2 face or half and half. The painted ones are still realy prety and some are worth the $ but it's just a coloring fluke not a freakish twin thing like with the 2 face nems.
I Cant wait to see that nem setteled in and opened up that is a super nice one. I have been meaning to get a two face for a while. That is a fine looking little nem. ALSO CYPHASTREA WOOOOOO! I wana see. I'm rather partial to those too.