A miniature lantern timepiece with alarm made around 1726 by George Graham of Fleet Street, London. The chapter ring is typical of Graham’s house style with Roman numerals, lozenge half-hour markers and arrows engraved on the inner quarter hour marks to accentuate the hour and half-hour positions. The dial centre is signed amongst scrolling foliate engraving with an alarm setting disk and pierced blued-steel hand.

The movement is weight-driven and of 30-hour duration with a verge escapement. There are threaded holes in the pallets, suggesting that the escapement was once fitted with small springs to help silence the ticking of the clock. This clock would have been used to wake the astronomer or assistant when they needed to make an observation during the night.

Graham continued to apply serial numbers to clocks and watches in the same manner that was established by Thomas Tompion (1639-1713) in the early 1680s. This clock is numbered 667, which suggests a date of manufacture around the mid-1720s and that it was probably purchased for use at the Royal Observatory as a refurbished item. In 1748 the third Astronomer Royal, James Bradley, purchased a chamber alarum from George Graham along with the transit clock, known as Graham 3. This clock along was sold to the Antiques trade in 1932 along with several other horological items.