The first time in his own solo-titled series, Swamp Thing #1 features the origin of Swamp Thing, the 1st appearance of Alec and Linda Holland, and the 1st appearance of Lieutenant Matt Cable.  This Bronze Age key is brought to us by Len Wein and beautifully illustrated by Bernie Wrightson.  The book is graded 9.6 NM+ with white pages by CGC.  It's a very nice copy!