Underground Comix are known for using different prices, covers (art or color variations) and interior content to distinguish different printings.
1st print August 1981 has 1.50 USD cover price and says 54321 on inside front cover.
This IS the 2nd Omaha story/appearance, Omaha first saw the light of day (1st appearance) in 1979 in the comics magazine Vootie.
Back cover advertisement for Dope Comix from Kitchen Sink Press. Includes cover to Dope Comix (Kitchen Sink Press, 1978 series) #4 February 1981.