This wonderful unusual pin appears to be some sort of resin or natural substance with the solid brown on top, a reticulated like fiber next and tiny minute bubbles in back. I spent quite a bit of time trying to research what the material is but had no luck. With the bubble like design in back make me think is a poured resin of some kind.
Approx. measurements are 3 3/4" long by 3/4" wide.
Great vintage condition with age appropriate light surface scratches.
Really a wonderful and unusual vintage bar pin.