Coins, medals and watches worth over £50,000 have been stolen as a series of museum break-ins continues.
The raid took place sometime between May 2 and June 19 at the storage facility used by Derby Museum and Art Gallery.
Among the haul was a collection of about 20 gold and silver watches from the 18th and 19th centuries, worth up to £3000 each, including examples made by clockmaker and scientist John Whitehurst, a member of the Midlands-based Lunar Society and a contemporary of Derby artist Joseph Wright. Some of the coins dated back more than 800 years.
The items were locked away for exhibitions and special viewings and with no sign of a break-in police say it is possible there was some inside knowledge involved. The theft was discovered when another museum asked to borrow some items.
Anyone with information should call police on 101 or Crimestoppers anonymously on 0800 555 11.
• Three men and a boy have admitted their part in the Fitzwilliam Museum theft - but the Chinese hardstone carvings taken remain missing.
The Cambridge museum was broken into on April 13 and 18 items, mostly Ming and Qing dynasty jades which had been part of the permanent collection for over 50 years, were stolen.
On Monday, July 30, at Cambridge Crown Court, a 15-year-old boy from London pleaded guilty to burglary.
Robert Smith, 24, of Hockenden Lane, Kent, and Steven Coughlan, 26, and 29-year-old Patrick Kiely, both of Eleanor Street, East London, admitted conspiracy to burgle.
All four will be sentenced on September 28 at the same court.