One of the most important auctions of timepieces in recent years was scheduled for Oct. 13-15, when Sotheby’s in New York City planned to sell more than 1,250 items from The Time Museum. These are “treasures from the greatest private American collection of timepieces ever formed,” said Daryn Schnipper, director of Sotheby’s Worldwide Watches and Clocks department. This sale, and three previous ones since 1999 of Time Museum holdings, “will be remembered for years to come as galvanic events in this field,” she added. The Time Museum was put together by Seth Atwood, a businessman from Rockford, Ill., over some 30 years and included important watches, clocks, chronometers, wristwatches, scientific instruments, and horological curiosities.

The three previous sales of The Time Museum’s items by Sotheby’s raised a combined total of $39,764,589. This sale was expected to bring in between $8 million and $10 million.

Highlights include three lots connected with John Harrison and the “Longitude Prize,” established in the 18th century by the British Parliament to encourage clock and instrument makers to find a way to determine longitude at sea, then a major scientific problem. The winner was Harrison, an ingenious clockmaker who devoted his life to solving that problem. The three items are the Precision Regulator (1725), the only known example of Harrison’s work outside England (pre-sale estimate: $500,000 to $1 million); a full-scale working model of his first sea-clock (pre-sale estimate: $65,000 to $100,000); and the famous Marine Timekeeper of Thomas Mudge, another competitor for the prize (pre-sale estimate: $1.5 million to $2.5 million).

Also being sold are a massive Astronomical and World Time Clock (1895), with 15,000 parts—created by a German mathematics professor who spent 30 years building it—and most of The Time Museum’s collection of chronometers.