German archives officials said Tuesday that they were unlikely to be able to afford to buy a major hoard of historic documents about Nazi dictator Adolf Hitler which comes up for auction at the end of this week.

The seven binders of papers were accumulated by prison authorities when Hitler was serving 13 months in jail 1923-24 and writing his book Mein Kampf. An auctioneer in the Nuremberg suburb of Fuerth says the minimum bid Friday will be 25,000 euros ($30,000).

The Bavarian State Archives in Munich said it had authenticated the documents, but declined to say whether it would bid for them.

"This is a high price," said director Peter Fleischmann who personally inspected the documents last week. He voiced concern that the papers might not be available to scholars, saying, "We are historians and we regard these papers as historical evidence."

According to auctioneer Werner Behringer, the unidentified vendor explained that his late father had found the collection in a job lot of books bought in the 1970s at a German second-hand sale. Behringer said he expected US collectors to lead the bidding.

Archivist Fleischmann said the papers were not vital to telling the story of the soft treatment the future dictator received while he was serving time in Landsberg Prison for treason after mounting a putsch, or unsuccessful coup. But they did yield new details.

"Some things were not known before this, such as how much time each visitor spent with Hitler," he said.

Hitler was allowed to meet a stream of 350 Nazi supporters, many of them highly placed. The chief of the prison near Munich engineered parole for the top Nazi after only 13 months of the 5-year sentence, praising his "modest and polite behavior."

Hitler was democratically elected German chancellor in 1933 and made himself dictator. He committed suicide in 1945 after the Second World War and Holocaust.

Another potential government bidder, the Munich Institute of Contemporary History, said the asking price for the papers was "very high." A spokesman, Bernhard Gotto, said this had put the institute off taking a closer look, but it had received three images of them.

"The scans we saw did not contain any information that altered our knowledge about Hitler's detention in Landsberg," said Gotto.

Collectors of Hitler memorabilia in Germany are at risk of prosecution if their activity seems to glorify the Nazis. Public display of Nazi symbols is a criminal offense in Germany.