A message in a bottle, which has floated on the waves of time for 90 years, has been found by French archaeologists.

The beer bottle contained a letter sent to an American soldier fighting in the First World War from his "Aunt Pete" in Oklahoma City. It was discovered by accident by archaeologists exploring a 6th and 7th century Merovingian settlement, at Messein in Lorraine.

The letter gives a jaunty, unthinkingly racist account of life in the US Midwest in July 1918, four months before the end of the war. "Its [sic] all most [sic] impossible to get help of any kind and those you do get are likely to be called any time," Aunt Pete writes. "There is a big bunch of darkeys going tomorrow night. They had a big parade today and are going to have a big dance tomorrow at the colored park: we lost our porter."

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The letter appears to have reached Sergeant Morres Vickers Liepman, of D Battery, 130th Field Artillery, who was serving with the 35th Division of the American expeditionary force in Lorraine.

Sgt Liepman, who survived the war, placed the letter in the bottle and buried it. He may have been trying to preserve it during a German bombardment.

The bottle had previously held Champigneulles, a local beer. It was still equipped with its mechanical closing system. The envelope and four pages were almost perfectly preserved. The bottle was found by a team working for a French government agency, L'Institut National de Recherches Archéologiques Preventives (Inrap), which explores important archaeological sites on which development is planned.

Officials from Inrap have tried to trace Sgt Liepman's descendants without success. The US embassy in Paris has discovered that Morres V Liepman studied in Pittsburgh, Kansas, and enlisted on 25 July 1917. He reached Le Havre in June 1918 and fought in the battles of the Argonne, Saint-Mihiel and the Vosges. In the autumn of 1918 his unit was stationed in the Haye Forest sector not far from the Noires terres where his letter was found. He returned to the US in 1919.

Aunt Pete's second name is unknown. The only address on her letter is that of the Robert M Scott drugstore in Oklahoma City.

* Inrap would be pleased to receive any more information on Sgt Liepman or Aunt Pete. The information officer, Mahaut Tyrrell, can be contacted on mahaut.tyrrell@inrap.fr.

Other extracts from the letter include:

My Dear Morres,

Well I guess you didn't know you were sending me a birthday letter you wrote me June the 8th and I got it July 8th. Say, don't ever again write on both sides of the paper for your letter was all cut up – you see where they cut out what they didn't want poor me to know, they cut out the other side too....

I wish you could hear Louise talk French. Her teacher says she is the best in the class ...

It is so hot here that you could cook eggs in the sand. Gee, Morres, I wish I could visit you now. It sure would be some trip. Robert says he would like to see it all, but he don't think he would like to get in the war... Well write me when you can. With heaps of love from the family and best wishes.

From Aunt Pete