I purchased this insulator at the Saratoga Springs National many years ago. I went through all the boxes a dealer had under his table. It was in the bottom of the last box. Got for only $90! The zinc cap is embossed PAT JAN 23 72. [id=246496230] [id=212669232] I have not seen another Ponds with the embossed cap. I've asked many people and no one recalls ever seeing one. The Smithsonian has several Ponds in their collection but none have the embossed cap. However, Bob Wilson had on at one time. [id=246496352] Here is a link to the patent: http://reference.insulators.info/patents/detail/?patent=U-122961