If the vendor said it was C. Walkeriana I would assume that it is. It has the classic Walkeriana shape. But I've seen many crosses that also inherit that shape flower so it's difficult to know for sure. Walkeriana is a great orchid because of it's compact foliage, nice size flowers and wonderful fragrance. Enjoy.
Do you have a photo of the plant with flower ???
For it to be walkeriana, the flower needs to be coming from a separate shoot directly from the rhyzome. If the flower is coming from the top of the pseudobulb its a hybrid and not the species walkeriana.