This is vintage new old stock (NOS) from the Sherms Magic Company in Connecticut.
A fan of four kings is displayed. One of the kings is exchanged with the Ace of Spades and the cards are squared up. When shown again the kings have changed into a fan of four aces! Now one of the aces is exchanged with a blank face card. The cards are squared and when shown again are all completely blank!
Very easy to do. You receive all the specially printed cards and instructions.
Note: Even though these are new old stock (and have never been used) they were manufactured at a time when it appears that printing procedures left something to be desired. Your set of cards may have some small inclusion spots here and there and sometimes a little smudging. But nothing too terrible. It’s just the way they were created at that time. You can still perform the effect with no problems.