Vintage bolo shown in Native American artists Volume 1

A stunning Rainbow Man bolo, very vintage, artist unknown and published in American Indian Jewelry 1, by Gregory Schaaf and Angie Schaaf. Published 2003. Volume 5, p22. This bolo is made from tortoise shell (not allowed to be sold in every state), turquoise, coral, mother of pearl and jet.Sterling silver, huge. Measurements are appx 4" in length or appx 102 mm and the width at the widest part is appx 3 1/2" or appx 88.9mm. The verso side has the following engraving SWD and MEL-536. I have the pictures of the hallmark in the photos. Can't identify the engraving is it the artist or the owner? Total length of the bolo strap is 40" or 1016mm. You can just see the era of work, where everything is handcut and placed with slight flaws and character. Circa probably 1950's. Hallmarked but unknown. The bolo on the neck is in a different light. Pre owned. Great condition.  This has tortoise shell in the bolo please contact Carole for purchasing as it can't be shipped to every state.