Correct me if I am wrong (it has happened at least once
) "Borneo", "Eureka", "Charles E" and "Commander" were a few of the 20 or so collected plants from the Collinette Expedition in the early 1960's. This expedition was the first post WW2 collection of rothschildianum. I think "Rex" is a seed raised clone, but I could be wrong on that. Rex is not the "best" flower, but is has fabulous vigor, and is relatively free and easy bloomer. The flower on "Rex" is good enough that the other traits make it the most sought after by breeders.