Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
1st print January (actually February) 1973 has 0.50 USD cover price.
2nd print October 1973 has 1.00 USD cover price.
3rd print April 1976(?) has 1.00 USD cover price and says "2nd print 4/76".