From 1712 until about 1718, a “duty stamp” was placed on one card in each deck to prove that duty tax had been paid after the wrapper had been discarded. Initially, no standards specified which card would be stamped.
Because the Aces had the most white space of any card, the duty stamp was usually made on one of them. The customary order of cards in a new deck has the Ace of Spades on the face (the top, if the deck is held face-up), so the Ace of Spades was the card most often stamped.
In 1765, the Tax Office began printing Aces of Spades. Playing card manufacturers were not allowed to sell their own. It was a capital offense to forge an Ace of Spades. The designs for the various taxes, based upon the cost of the pack of cards, had an enlarged spade pip in the center of the design. The large spade both clearly identified the card as the Ace of Spades and became part of the official stamp design. This is how the Ace of Spades got a big spade in the middle.
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