by Martin Armstrong, Armstrong Economics:

I have often been asked the question, WHY did the Greek denomination of the stater comply with the 8.6 frequency of the Economic Confidence Model? The silver stater minted at Corinth was 8.6 grams (0.28 oz) in weight, which was divided into three silver drachmae of 2.9 grams (0.093 oz). Its rival city-state was Athens, and their silver didrachm (two drachmae) weighed 8.6 grams (0.28 oz), while their Athenian silver tetradrachm (four drachmae) weighed 17.2 grams (0.55 oz).