East Germany will bid goodbye to an old currency by burying it in salt mines and feeding it to foundries, clearing the way for new cash and a radically different way of life. At the stroke of midnight Saturday, the 42-year-old East German mark of the ousted Communist regime will be replaced by one of the free market's most powerful forces, the West German mark. An East German who buys a beer with his old money in the minutes before midnight could have his change brought back in West German marks, so quick is this change to take place. That modest event would signal the economic unification of the two German states, the end of four decades of East German socialism and the de facto creation of a single Germany. The West German state bank, the Bundesbank, has trucked in 25 billion uncirculated West German marks, said spokesman Sigfried Guterman in Frankfurt. ``Transporting money is our business,'' he said Wednesday. ``This was a little more complicated.'' Guterman said heavily guarded trucks from Bundesbank offices throughout West Germany brought 600 tons of paper money _ 400 million individual bills _ and 500 tons of coins during the past two months. The money was distributed to 15 different cities. The East German State Bank has been taking that money to 10,000 different locations, where it will be available to East Germans beginning Sunday. Long lines at banks nationwide continued as East Germans filled out forms to convert their savings accounts to West German marks. Guterman said there have been no major problems replacing one currency with another virtually overnight. The 25 billion in West German marks is new, uncirculated cash that should be enough to accomodate the nation, Guterman said. East Germany now only has 12.3 billion East German marks in circulation, said Bernd Schroeter, spokesman for the East German State Bank. All citizens will be asked to deposit their remaining East German cash in banks by July 6. There, it is to be counted, sorted and wrapped. After final inventory, the bills will be stored in salt mines pending their later destruction, Schroeter said. East Germany is not equipped to burn large amounts of bills in environmentally safe ways, he said. Guterman said East Germany might have to use the Bundesbank facilities to burn the money. Most of the coins are pure aluminum _ which drew chuckles from Westerners _ and two denominations are in copper. Schroeter said these will be melted down and recycled. The East German currency is small and flimsy compared with the large West German bills. The 50-mark bill carries the picture of Friedrich Engels, who with Karl Marx drafted the blueprint for modern socialism. The back depicts a giant factory spewing smoke. The East German currency was non-convertible and virtually worthless outside the East bloc. After the East German revolt last autumn, it was traded on the black market at a 20-1 rate for West German money. Now, small savings accounts will be traded at a 1-1 rate, with larger amounts converted at a 2-1 rate. The Bundesbank has been planning a new West German currency for years, and will begin circulating some notes on Oct. 1. By the end of the next year, Guterman said, all the current money will be replaced. Concidentally, one of the first bills that goes into circulation on Oct. 1 _ the 100 mark note _ will depict the East German city of Leipzig. ``It is more or less by accident,'' Guterman said. ``Nobody knew there would be a currency union when these bills were designed.'' Leipzig is on the back of the bill because it is the birthplace of the person on the front, 19th century German pianist Clara Schumann. Leipzig is also the home of the an East German currency mint, and Guterman said it will be used to print part of the new 5 mark note.