This is the number of karats representing 100% pure gold
It is an extension of the older karat system of denoting the purity 
of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24
)... [DOC] [TLE] Gold Purity Guide: Difference between 24k, 22k and 18k gold [PAR] Karat is basically a unit used to measure the purity of gold.