Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
1st print 1972 has 0.50 USD cover price. Published by Rip Off Press with Rip Off Press logo on cover.
2nd print June 1973 has 0.50 USD cover price. Has Last Gasp logo.
3rd print November 1973 has 0.50 USD cover price. Believed indistinquisable from 2nd print.
Sequence on inside of back cover.