Plethron
The Plethron was an ancient Greek measure of length and also a measure of the same name Ackermaß.
Length
Surface
As square measure Plethron it would have been more accurate to call with square Plethron.
The larger measure was the Defsätine that corresponded 11.466 Plethren. The Plethron was replaced by the modern Greek Ackermaß stremma.
The Defsätine now had 11.76 Stremen.