I read once that a spanish mint cracked a coin die and the assistant there used a die that was out of date in the future. the old dies had to be destroyed after they finished minting so it could be possible that a future die was used before that year arrived.
Hmmm, possibly, but I think it was usually the other way around- saving a set of old dies and clandestinely taking them out later to strike coins that were debased or below the proper weight.
Probably the best example of this were the Massachusetts issue oak tree and pine tree shillings. No matter what date they were struck on, they always say 1652 or earlier, because that was when the King of England told them to stop minting them.
Why did the colonial gold and silver designs change so quickly? There is a well documented case of this at Potosi, in that they went to a different die design and called in or countermarked all the old coins becuase of a mint scandal. But there are other times the coins changed, and it may reflect something taking place that affected the internal behavior of the colonial mints. An example of this would be the many dots added to Lima escudos after about 1718.