This round SCA Lightning Rod Ball is embossed on the side, near the center: PATd JULY 77 this also refers to the patent issued to Charles Smith of Chicago, IL for a glass LRB. Patent linked here: http://reference.insulators.info/patents/detail/?patent=U-192628 Like most SCA LRBs, this was likely made with a mirrored coating on the interior of the ball. Thus when up in the air it was reflective. The 'mercury' coating usually eroded with air and water seeping inside the ball.