Not much is known about these, they were issued both with and without "Wills` Cigarettes" to the front, (which explains the b above - b being the ones without the Wills on) and plain back cards with on the front also exist, though they are thought to be cut from partially printed sheets.
Purple Mountain was actually also used as a brand by British American Tobacco, and perhaps these are the ones without the Wills on the front. There is also a set of Purple Mountain "Flowers", which is sometimes called Chrysanthemums" so presumably these are the most featured in the set.
The packet was presumably the same design as appears on the back of the cards, but the mountain depicted looks rather strange, more like an artists impression of a mountain, unless anyone knows of a candidate? There is a Purple Mountain, in China, near Nanking, but I will have to look at that tomorrow.