I am estimating that this item is from the early 1960's, though it may be late 1950's. Max Andrews ran Vampire Magic in the UK from the 1950's thru the 1970's. Vampire was a dominant force in magic, and so items from it's lineup are highly prized and sought-after.
This set of Diminishing Cards uses the Chappender method, which (if you have seen Tenyo's Diminishing cards, or most other sets) is similar and has become the classic method for working this effect. It is a shame this effect is not performed as often anymore, because it is very visual and very entertaining. That said, you probably will not use this Vampire set to perform with. The cards are fairly crudely constructed when compared to today's standards of printing.
But as a collectible, this is a rare find. The card set is complete, and the original instructions and package envelope are included. The envelope is a bit frayed around the edges, but considering it's 60-70 years old, it is in very good shape. Only one available.