Pictures and historical artefacts have been stolen from a World War One heritage centre in Newtownards.
The theft at the Somme Heritage Centre on the Bangor Road was reported to police at about 12:35 GMT on Saturday.
Two men, who had paid in to the centre, removed glass panels on displays and stole items.
Many of the items relate to the 1913 Home Rule Crisis and the original Ulster Volunteer Force. Together they would be worth thousands of pounds.
Carol Walker, the director of the Somme Association, said: "They had removed glass panels from two of our exhibition cabinets and stolen memorabilia and artefacts relating to the Ulster Volunteer Force of 1913.
"They would be valuable at a cost as well as a price, but more so for us as a museum it's the history, the story that they tell."
The centre examines Ireland's role in WW1, especially the involvement of the Irish volunteer Divisions: the 10th and 16th (Irish) and the 36th (Ulster), as well as contemporary events such as the Home Rule Crisis and formation of the UVF.
It is believed a black car was used by the thieves.
Police have appealed for anyone who has any information about the incident to contact detectives at Newtownards on 0845 600 8000.