In a late 1960's or early 1970's there was an article in Gun Digest that illustrated and discussed a number of inlays and their meaning. Many seem to be based on what I'll call (probably incorrectly) Pennsylvania Dutch folk art, with the same figures appearing on barns, quilts, painted furniture, etc.
My young self was enthralled by the article. My older self questions the scholarship that went into the article. That issue of Gun Digest is with some of my other books in Minnesota. I can provide the specific year and author's name when I head back up for the Fourth if you'd like.