LienLiu did a nice paper on rothschildianum, maybe he has his data handy. I am working from memory, perhaps Lien will correct me if I am wrong.
rothschildianum "Mont Milais' FCC/RHS was exhibited by the Eric Young Orchid foundation. It was a large flower, on a large plant, the flower was over 30 cm natural spread. Not small. The plant is not small either. It is famous for it's good size, and BOLD color contrast. Its background is fairly light, close to white and the stripes are deep red-brown. So the visual effect is quite bold. Many roths have a base color that is almost yellow, so the stripes don't pop as much visually. The other thing that really made Mount Milais famous was its owner, EYOF. They knew how to put the plant to good use, and promoted it. They also shared pollen with W. Robert Weltz and with Terry Root and Wharton Sincler. Hence the cross "Rex' x 'Mont Milais'. Rex was the very large collected rothschildianum that belonged to Rex van Delden (at one time Paph breeder at Stewarts Orchids) before he sold it to Orchid Zone.
'Mont Milais' is the clone of choice for a roth with bold colors, good form, large flower and medium large plant habit. Definitely one of the best of the era.
'Borneo' is the clone of rothschildianum that blooms on a small plant, often with just a single flower. 'Borneo' was awarded with a 28 cm flower, which is on the medium - small side for current awards. Colors of markings are very dark, over a butter yellow backgound, so the striping can look almost muddy. A blooming on a multigrowth plant will have 3 or 4 blooms. A good roth, but the new seedlings coming up will be so much better.
'Rex' is one of the most vigorous of the roths, and large too. These traits are passed on to its offspring.
'Janet' is the clone from Lee & Janet Kuhn, a collected plant originally exhibited as Paph elliotianum. This is a very vigorous clone, with a large flower, ~30 cm natural spread, but the petals and dorsal are a little bit narrow. This plant could have become as famous as 'Rex' but was not 'promoted' nor used in breeding as expertly. Then in the mid 1990's an unscrupulous varmint sold divisions of a mediocre roth; deliberately mis-labeled as 'Janet'. So there are a few real divisions floating around, and many more 'fakes' floating around.
Today IMHO the best roths for the 2010 to 2020 generation will be from several of the seedling crosses made by Sam Tsui of the Orchid Inn.
now I need to get back to work.