A Christogram is a combination of letters that forms an abbreviation for the Holy Name of Jesus. In the Middle Ages the Name of Jesus was written: IH-E-S-U-S. IHS is an example of the first and last letters of the Holy Name. At this time, the letter "I" was either a vowel or a consonant. The letter "J" is the modern convention for the consonant form of "I". The Latin-alphabet letters "I" and "J" were not systematically distinguished until the 17th century. The earliest example of this Christogram thus found was on this tenth century Byzantine gold coin. Please note "IHS XPS REX", which is a Greek abbreviation for "Jesus Christ King".