Vintage DURO ventilated, visible porcelain spark plug

Up for auction is a 7/8” thread, used, DURO spark plug with holes formed into the porcelain. These holes I believe were both cooling holes and possibly spark observation points. Please note if you are a winning bidder from other than USA , I will forward you an invoice for shipping charges after getting your mailing info. Also be advised of import duties, taxes and charges (typically collected upon delivery or pickup) are the buyer’s responsibility and are NOT included in the item price or shipping charges. Please check with your country’s customs office prior to bidding/buying to determine what these additional costs will be. I always mail out items to USA with USPS delivery confirmation number and email the winner with info.