One of the rescued postcards, with the figure of a man clearly visible.

Experts are examining a collection of postcards and photographs rescued from the wreck of a German cruiser in Scapa Flow.

The images were recovered from SMS Karlsruhe a First World War cruiser, after recreational diver spotted them on the wreck and passed the information to Historic Scotland.

The Karlsruhe was one of the seven battleships and cruisers of the German High Seas Fleet that were scuttled in 1919 following the surrender of Germany after the First World War.

They were scheduled as ancient monuments by Historic Scotland in 2001 to give them full legal protection whilst still allowing divers to visit the wrecks without the special licence required for other protected wrecks. It is a criminal offence to damage a scheduled ancient monument.

A preliminary dive was carried out in October 2003 to bring up a small number of the papers to test that conservation was possible. This operation was successful and Historic Scotland contracted local company SULA Diving to retrieve the rest of the photographs.

Bobby Forbes of SULA Diving said: "The postcards had been kept in tin boxes which have gradually eroded, explaining why they have lasted so long under water. The corrosion from the boxes welded the stacks together and it was a very delicate operation to separate them."

Deirdre Cameron, Inspector of Ancient Monuments at Historic Scotland is in charge of the project.

"The paper, some 15 stacks of it, is now with a special conservation laboratory where they will be separated, the sediment sluiced off and conserved. Once this is done the images will be clearer and it should be easier to identify," she said. "We will also know just how many items we are dealing with. A conservative estimate would be 100 to 200 cards.

"There are a lot of people who collect this memorabilia and I am hoping that someone out there will recognise the type of postcard or photograph that we have and be able help us learn more about them."