Thread:Hatebunny/@comment-1038387-20150526124010/@comment-3361105-20150526125827

according to Swamp Thing: Book Three (which is where I got it from), "This portrait was used as the first of six foil-stamped chase cards in the vertigo trading Card set released by SkyBox in 1994."

... or you could just source it to the third Saga of the Swamp Thing collection.