Dear Raymond,
the name Paphiopedilum robinsonii is nowerdays really a synonym of Paph. bullenianum.
The plants which were cultivated a long time as Paph. robinsonii were decribed newly as Paph. cerveranum and later new classified as Paph. appletonianum var. cerveranum. The difference is especially to see in the staminode.
Here an example of Paph. appletonianum var. cerveranum.
Here the typical staminode, different from all typical form of Paph. appletonianum