This is an intriguing hybrid apparently made between B. vittata and an unknown Billbergia. We know that in any hybrid involving B. vittata the B. vittata dominates and I am always hesitant to link such a crossing with a species name.In Nov-Dec 1959 the Bromeliad Society Bulletin had a cover illustration done by Morris Henry Hobbs of a Billbergia 'Callophylla' (sic) which was later amended to B. vittata by the same person in the Mar/Apr Bulletin page 23. Note that Morris Henry Hobbs came from Florida whereas the hybrid B. 'Calophylla' originated in California.
If we carefully read James Giridlian's article in the Jan/Feb 1961 Bulletin we note that Atkinson had hybridised B. vittata with a plant then known as B. amoena. I feel sure that this must be linked to Atkinson 44 which became B. buchholtzii (see other article on this "species").
There is one little problem in that the name B. 'Calophylla' was only used by Atkinson for plants that he distributed. After his death plants were distributed by Evans and Reeves as B. enderi hybrids. Proper B. enderi became Quesnelia lateralis so there was a bit of mis-naming here.(Not uncommon I can assure you)
My experience in Australia is that some growers refuse to change the names on their labels even though in error and I am sure this same trait applies to Americans. Therefore, I believe that the names 'Calophylla' and 'Enderi' are still on some labels on plants in California that flower very similar to B. vittata. The label should not be changed to B. vittata but to B. 'Calophylla'.
BUT I would love a Californian to photograph one of these plants so that it can be held for posterity and put me out of my misery! I find a good place to find these "gems" is in small botanic gardens or deceased estates.
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