IMPORTANT: As of this writing, I am unable to locate a research document that lists or otherwise documents a "scalp belt" as an artifact made or used by a Native person or Native tribe. I have found many references to it in works of fiction by authors who are not Native. It appears, for example, in Zane Gray novels (a reader of the blog wrote to me with that information).
This is the illustration of the "scalp belt" in the 1973 edition of Caddie Woodlawn, with illustrations by Trina Schart Hyman. It is on page 152. The illustration from the older edition, with Seredy's illustrations, shows Indian John and Caddie and the "scalp belt" (see May 9th, below).
This is a close-up of the belt itself.