Complex sentence: This interruption in the Royal Mint's usually excellent quality control left numismatists excited as the last time an undated coin entered circulation was more than three hundred years previously, in 1672, when Charles II reigned.
Split into simpler sentences: This interruption in the Royal Mint's usually excellent quality control has left coin buffs excited. The last time an undated coin entered circulation was more than 300 years ago in 1672 when Charles II reigned.