Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
1st print July 1970 has 0.50 USD cover price. Has blue/purple cover.
2nd-3rd print have 0.50 USD cover price. Have purple/green cover. Believed indistinguishable from each other.
Sequence on inside of front cover with indicia information at bottom of page.