Typically this 1" celluloid is black on cream (often discolored) bkg. This bkg. is turquoise blue (even on the curl edges) except for 1/8" dot at left with tiny raised bump of clear celluloid. Only example we've seen. Glows intensely in dark with image and text easily seen. Curl has maker's name "Cruver Mfg. Co. Chicago." Cello surface on side edge has one pinhole and 1/8" stress line but both barely show and only from the side. Button was issued in 1939 and came with a member card titled "Secret Pledge Of The Shadow." The card pledge was to "Stamp Out The Forces Of Evil In This Land. I Shall Recognize Other Members Of The SHADOW SOCIETY By This Card And By The Magic Button Which Only Members My Posess." Although not marked as such, we believe the sponsor of this premium was Blue Coal. Most unusual and possibly unique.