"Blowhole," Caused by Contaminants / Improper Allow Mix in the Strip

Courtesy of Ken Potter.

A Blowhole, (a term borrowed from the welding trade), occurs when a defective blank is punched from an area of defective strip. The "holes" are caused by contaminants and or improper alloy mix.

This piece became ragged from the metal being recycled many times until contaminants were rolled into the strip. On this piece of strip, you can see both edges, the interior and the tail end are defective. A blank punched with the defect at the edge is often referred to as a Ragged Clip while one restricted to the interior is called a Blowhole.

Piece of the Strip That Would Make a Blowhole Blank/Planchet

Certified Blowhole Errors

Image Courtesy of Coin Community Members on eBay

1946-D Wheat Cent Blowhole

Certified Blowhole Errors

Image Courtesy of Coin Community Members on eBay

196x Lincoln Cent NGC MS-65 Blowhole

Certified Blowhole Errors

Image Courtesy of Coin Community Members on eBay