Very nice cover! I've never thought of myself as any kink of *oligist, but here's what I know about this issue:
It is part of a series called the Popol Vuh issues. They were released in four separate issues/themes during 1981 and include Scott #'s C715-C738. The themes are: 1 - The Creation; 2 - The Adventures of Hun Ahpu and Xbalanque; 3 - The Founding of the Quiche Nation; and, 4 - The Territorial Expansion of the Quiche. Although they are of several different colors and look similar, only two are greenish-yellow. I can't make out this particular illustration, but I believe the ones shown are either C727 (Destruction of the Stick-Men) or C729 (Chomiha, Wife of Balam Acab).
PhilB would probably be able to narrow it down more. BTW, here's a link with more information:
http://en.wikipedia.org/wiki/Maya_Hero_Twins