Well, Paul Gordon has solved all the issues and his deck contains 50 duplicate Ace of Spades and the four Kings. No routine supplied, but there are many standards "out there" for which you can use these beautiful top-quality linen-finish cards.
With The Ultimate Rainbow Deck, ALL the backs are different colors and/or styles. All same stock/size. All geometrical "classic look" back designs. This is one classy deck!