(JTA) — An auction house in Britain is investigating the authenticity of a letter billed as sent by a Nazi official and detailing Jewish transports during the Holocaust.

The letter details the transportation of 5,000 Jews daily to the Treblinka extermination camp and is to be auctioned off on August 21 by Mullock’s, an auctioneer in the Birmingham area, The Jewish Chronicle of London reported Friday.

“I shall be investigating this with the vendor and making enquiries. We are obviously putting it up for auction in good faith,” Mullock’s expert Richard Westwood-Brookes said. “If I can’t get to the bottom of this we will withdraw it pending further investigations.”

Dated 19 July 1942, the letter purportedly was sent by German railway boss Dr. Theodor Ganzenmuller to Karl Wolff, chief of staff for Heinrich Himmler, a leading figure in the Nazi party.

It was written in response to complaints by Himmler, the Final Solution’s architect, that the German railway authority was not efficient in transporting Jews to their deaths.

But the document, expected to fetch $930, is an almost identical copy of another well-documented letter used in evidence at the Nuremberg Trials, which is dated July 28 1942.

Ben Barkow, the director of the Wiener Library, one of the world’s most extensive archives on the Holocaust, told the Chronicle that the Mullock’s letter is troubling because its wording and grammar “are riddled with mistakes”.

“Without a satisfactory account of the history of this document since 1945, I believe that few historians would feel able to have confidence in its authenticity,” Barkow said.

The letter, according to the Chronicle, will be auctioned alongside Adolf Hitler’s personal copy of the German version of the “yellow pages” and a wedding-gift edition of Mein Kampf, the book written by the German dictator.

Postcards showing photographs of dead Jews in Auschwitz, taken by a Russian soldier, are among dozens of Nazi-related items expected to fetch a total of over $124,000.