i was also unsure of what mine was when i bought it but after seeing Copp's specimens and having his input , i too have a hybrid Rostratum= beautiful hardy fish imo and just as special as a pure Rostratum although i am partial to that blue line the pure Rostratum develops just below the dorsal fin.
<a href="http://www.flickr.com/photos/42085951@N06/4891002605/" title="Nikon d90 Black tang hybrid by Kinlayan, on Flickr"><img src="http://farm5.static.flickr.com/4121/4891002605_bb8b408808.jpg" width="500" height="332" alt="Nikon d90 Black tang hybrid"></a>