One of the USA’s rarest single stamps is the 1868 1¢ Benjamin Franklin Z-Grill. Printed and grilled in 1868, the Z-Grill design was not used for very long, a couple of weeks at the most. That short production time is what accounts for it being so rare today. As explained in a previous article, a grill was a waffle-like design embossed on a stamp as a security measure to prevent reuse. See article: FAQ-What is a stamp grill?
The Z-Grill is unique in a couple of ways. Firstly, it was the first grill to be put into production in 1868 (despite its later bearing the last letter of the alphabet as its name!). Secondly, its grill pattern differs from other grilled stamps. The ridge pattern of most grills is vertical, whereas the pattern on a Z-Grill runs horizontally.
There are only 2 known genuine examples of the 1868 1¢ Z-Grill. One of them is owned by the New York Public Library. The other is owned by billionaire Bill Gross. Mr. Gross traded his block of 4 «Inverted Jenny» stamps (another major rarity) with Donald Sundman (owner of Mystic Stamps) for his 1¢ Z-Grill. The exchange is whispered to have been worth $3 million USD (Sundman originally purchased the 1¢ Z-Grill for $935 000 USD in 1998). The Scott Catalogue presently lists a used 1868 1¢ Benjamin Franklin Z-Grill at $3 million USD! If and when Mr. Gross ever decides to sell the stamp, who knows what it would go for!
Another 1¢ Z-Grill will probably never be found. But other grills are almost as rare! Check out the Scott catalogue and keep your eyes peeled!