Belden was shown in a Lettergraphics ad in U&lc vol. 1, no. 3 from 1974, without design credits. It’s a constructivist design with slot-like counters and partly rounded corners. Turtle (Letraset, 1971) is a bit related, albeit much rounder and organic-looking. Berkmire AOE (Astigmatic, 2006) is a digitization of Belden that includes the original alternates and expands the character set.