This issue has variants.
Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
1st - 5th print are all 0.50 USD cover price.
1st print February (actually May) 1971 has ad for Thrilling Murder Comics on inside front cover.
2nd print has ad for "Posters by R. Crumb" added to inside front cover.
3rd print has "Eric Fromm has a 3-Foot Long One" on inside front cover.
4th print has matte cover? 5th print has glossy cover? Both have Apex Novelties poster ad on inside of front cover.
6th print has 0.75 USD cover price with "Apex Treasury of Underground Comics" on inside front cover.
7th print has 0.75 USD cover price with "Classics in their own time" ad on inside front cover.
Inside front cover ad that differs in later printings.
"Dedicated to my good ol' Uncle Pete"
Image on back cover of issue.