Nancy Cabot illustrated this block in August, 1934, where she says that many quilt patterns were originally adapted from native American designs. There is another gorgeous NAVAJO block Cabot published as well in September 1935 in Jinny Beyer, #123-4). The 1885 blanket illustrated upper left (which might also inspire the full quilt) is housed at the University of Iowa Museum of Art.

As they say, if you're into it, you're into it — a huge, breathtaking array of Navaho blanket patterns is available at Google Images. For more historical information, with Navajo quilt-like geometry, see The Early History of the Navajo Blanket.