This insulator contains a threadless pinhole with two opposing slots for a wedged wood pin arrangement designed and patented by Samuel Oakman. This unique pinhole design and unusual embossing location makes this relic very popular with collectors. Great condition with a clean surface and good clarity to the glass. .CD No.: 728.7 EMBOSSING: (base of pinhole) Oakman's Patent July 26 1870 .... http://www.in-glass.com/direct/7287OAK010Aqua.htm ... $1,799.00 ... for other great items see ... http://www.in-glass.com/direct/