Sunday is the 20th anniversary of the founding of Poland's Solidarity Trade Union, which led, by domino effect, to the end of one-party rule, not just in Poland, but throughout the Eastern Bloc.
For Poles, the true birthday falls two weeks earlier, on August 31, when the Gdansk Accords were signed between the Polish government and striking shipyard workers led by an unemployed electrician called Lech Walesa.
Yet last month, as Poland prepared to celebrate the anniversary, it was discovered that neither the government nor the Solidarity copy of the agreement could be located.
This is like mislaying the Magna Carta or the Declaration of Independence. Although most of the strikers' demands dealt with economic grievances, they included the right to independent trade unions, free from the control of government and party.
Stanislaw Gomulka, reader in economics at the London School of Economics, said: "Although Solidarity was a trade union, it was the political demands of its members that accelerated the break-up of the communist system throughout Europe and the Soviet Union."
The significance of the original documents is debatable. Leszek Kowakowski, emeritus fellow of All Souls College, Oxford, said: "If you have copies of a document, then the loss of the original is not a matter of historical inquiry, but of emotional attachment."
Dr Gomulka thinks there is a strong chance they might turn up. The huge bulk of government and party papers from the period has not yet been sorted out. Moreover, when martial law was declared and the leaders of Solidarity interned, some rank-and-file members managed to hide some of the most vital Solidarity documents before the authorities could seize them.
But they hid them too well - a few weeks ago a bundle of papers came to light in the hollow of a house wall in Gdansk. The accords were not among them, but the find has raised hopes of other discoveries. "If not," Dr Gomulka said, "the tablets with the Ten Commandments have been missing for more than 2,000 years, but that does not make them irrelevant."