Benjamin Franklin Z Grill Stamp: Only Two Known

The 1868 one-cent Benjamin Franklin with a Z grill, Scott 85A, is the rarest United States postage stamp: only two are known to exist. One belongs to the Benjamin Miller collection at the New York Public Library and has been on loan to the Smithsonian National Postal Museum, so it will not be sold. The other is the only one a collector can own.

That single stamp sold for US$4,366,000 at Robert A. Siegel Auction Galleries on 14 June 2024, as part of the William H. Gross collection sale that made about US$19.2 million in all. Bidding opened at US$3,000,000 and three bidders pushed the hammer to US$3,700,000; the 18 per cent buyer's premium brought the total to the final figure. It more than doubled the previous record for a US stamp.

Its price history reads like a record of the whole American market: US$42,500 in 1975, US$90,000 in 1977, US$418,000 in 1986 and US$935,000 in 1998, when Mystic Stamp Company bought it and set a US record at the time.

In the late 1860s the Post Office Department was losing money to people who washed the cancellation ink off used stamps and posted them again. The answer was a grill: a roller studded with small pyramids that pressed a waffle pattern into the stamp paper. The broken fibres absorbed the cancelling ink deeply enough that it could not be washed out.

Several grill types were tried in rapid succession and each was later assigned a letter by catalogue editors. The Z grill is distinguished by the direction of the ridges: on a Z grill the ridges run horizontally, where every other grill type has vertical ridges. The grilled area measures roughly 11 by 14 millimetres.

Z grills were in use for only a short period — the earliest known postmarks on Z-grilled stamps are from January 1868 — before the pattern changed again. That brief window is why so few exist. The same grill appears on the two-cent Jackson, three-cent Washington, ten-cent, twelve-cent and fifteen-cent values, all of them scarce, with the fifteen-cent Lincoln (Scott 85F) also known in just two examples; one made US$2,773,000 in the same June 2024 sale.

In late 2005 the financier Bill Gross wanted a complete collection of nineteenth-century US stamps, and the Z grill was the one piece he could not buy, because Mystic Stamp Company's president Don Sundman owned it and was not selling for cash.

What Sundman wanted was the unique Inverted Jenny plate block of four, which Gross had bought at Siegel in October 2005 for US$2,970,000. The two men swapped: the plate block went to Mystic, the Z grill went to Gross, and both items were valued at roughly three million dollars.

That exchange put the Z grill into the collection that came to auction in June 2024, where an anonymous buyer paid US$4,366,000 for it. The block Gross gave up is still the only Inverted Jenny plate block in existence.

A grill is examined from the back of the stamp, in raking light from a low angle, so the pressed pyramids throw small shadows. The examiner counts the rows of points across and down, measures the grilled area, and notes whether the ridges run horizontally or vertically. On a genuine grill the points break the paper fibres, which shows as a change in texture rather than just an impression.

Because the difference between a common stamp and a five-figure or seven-figure one can be a few millimetres of grill, faking is routine. Common methods include pressing a fake grill into an ungrilled stamp, enlarging or reshaping an existing grill, and photographing the back to suggest points that are not there.

No grilled rarity should be bought without a current certificate from a recognised expertising body, and any 1867–68 stamp described as carrying a scarce grill without one should be assumed to be an ordinary example. Our guide to stamp errors and varieties explains where catalogue-recognised varieties end and wishful thinking begins.

The 1861–68 one-cent Franklin design was printed in very large numbers and most examples are ordinary stamps worth a few dollars. The grill, the perforation measurement and the shade are what separate the common ones from the scarce ones, and none of those can be judged from a photograph of the front alone.

Sensible order of work: identify the design and series first, then look at the back in raking light for any grill impression, then measure the perforations, then consider condition. Our US definitive stamp identifier covers the series and their design details, and perforations and watermarks covers the measurements.

Photograph the stamp and the app identifies it, which gives you the series and catalogue number to start from.