Underground Comix are known for using different prices, covers (art or color variations) and interior content to distinguish between printings.
1st print June 1973 has 0.50 USD cover price and no(?) '(c) 1973 by R. Crumb' at bottom of inside front cover.
2nd print has 0.50 USD cover price and has '(c) by R. Crumb' at bottom of inside front cover.
3rd print has 0.75 USD cover price and has '(c) by R. Crumb' at bottom of inside front cover.