20 YEARS

The yellow store front rises four stories like an exclamation point opposite a squat while hut crowned by an American flag, the United States Army Checkpoint Charlie. The house, the last one on Friedrichstrasse in the West, sits on the doorstep of the world's largest fenced-in concentration camp.

Twenty-five yards from the house, slicing Zimmerstrasse's middle, is the wall , a 12-foot-high curtain of concrete that separates the two Germanys and divides Berlin in a serpentine squiggle along the Soviet-sector border.

On the other side of the wall, 17 million East Germans live under the Soviet fist, in roughly the acreage of Ohio with a combined population of Pennsylvania and Maryland.

The Russians have stationed 400,000 troops in East Germany, augmented by 200, 000 soldiers of the German Democratic Republic. About 14,000 of these are deployed at the border.

On Aug. 13, this division between German and German, Berliner and Berliner, will be 20 years old, nearly a generation in human terms.

The House of Checkpoint Charlie is permeated by the ghosts of the thousands of East Berliners, East Germans, and people of the Eastern-bloc countries who have died in their attempt to escape. Some of their pictures are plastered on the walls of this, the only museum about the infamous wall.

But the house is also a monument to the thousands who escaped to freedom in the West, as well as an inspiration (and a warning) to those thousands still on the other side of the wall who dream of escaping.

The desire for freedom is ever present in the museum. Every one of the 25 exhibits testifies to the ingenuity of people striving for freedom. Some flew over the wall; others burrowed under it; some swam across the frontier; and at least one refugee swam underwater to the West.

Not a few devised ways to be transported past the border guards -- inside mechanical equipment, inside gas tanks, under cars, embedded in the upholstery of buses. Some leaped to freedom into jumping-sheets held by fireman -- some missed the jumping-sheet and crashed onto the paving stones.

Many would-be escapees who challenged the guards and charged the wall were shot and left to die before they reached the summit. Others reached the summit, only to be shot and fall back into bondage.

This bit of the wall at the checkpoint faces the American sector. Many have died here ever since that August Sunday in 1961 when the wall (then mostly barbed wire reinforced with gun-toting East German soldiers and People's Police, backstopped by Soviet military) appeared overnight.

And this is why Dr. Rainer Hilderbrandt, the director of the museum at Checkpoint Charlie, chose this site on Friedrichstrasse to commemorate the daring of the men and women who defied leftover Stalinist policy to escape from the concentration camp.

"From the first day of the wall," says Dr. Hilderbrandt, a former inmate of Hitler's prisons, "we thought it's important to let the whole world know what here has happened. So we, all at once -- a group of experts, of refugees and of former GDR border guards -- we thought we must make an information place.

"We thought it best to make it at the Bernauerstrasse in the north where just the street becomes the front line, and where, from the windows, from even roofs, people jumped into West. . . and where, even yes, they landed dead."

And so, a few days after the wall went up, Dr. hilderbrandt and his newly formed Actiongroup August 13 went to Bernauerstrasse and assembled the bits and pieces of artifacts that were the beginnings of the museum in the House at Checkpoint Charlie.

The exhibition there was so successful, Dr. Hilderbrandt recalls, "that we thought we must go to the center of Berlin, that we must go to Checkpoint Charlie, where the Western powers and the Soviet powers and the two Germanys face each other."

Almost a year to the day after the wall appeared, the residents in the house of Checkpoint Charlie witnessed what was, and remains, one of the most notorious incidents in the history of the wall: the day an 18-year-old, shot by East German border guards as he scrambled up the wall, lay ensnared in the barbed wire for 50 minutes and bled to death, while crowds of West Berliners stood around helplessly, unable to reach him.

"Murderers!" screamed the West Berliners. Moments later, as vehicles carrying Soviet soldiers entered the West at Checkpoint Charlie, the frustrated crowd which had gathered pelted them with stones.West Berlin poice and American soldiers had to restrain them.

But nobody attempted to restrain an elderly man who, walking with a stoop and carrying a paintbrush, walked up to the wall in the Zimmerstrasse, three feet from where the young man had fallen on the other side. And there for the West Berlin crowd to see, he daubed the frightening letters KZ -- concentration camp -- on the rough cement.

Peter Fechter, at age 18, became the wall's 50th fatality.

What fueled these early desperate scrambles and leaps toward freedom?

"They would never have done this if they had not the experience of Nazi times ," Dr. Hilderbrandt believes. "The GDR government could not tell them from one day to the next what would happen to them. . . . It was just like a field in a concentration camp, you know. They had had this same experience from Nazi times , this feeling of isolation. People became nervous, they thought it was happening again -- Nazi times in similar form."

"They thought," Dr. Hilderbrandt explains," 'the earlier we leave the better. We do not know what will happen tomorrow.' As you say in English, 'They lost their heads.'"

Rainer Hilderbrandt remembers much about the violation of human rights -- his. He was twice imprisoned in Nazi Germany during World War II -- once for reading the wrong books and writing the wrong articles, and once for refusing to betray his friend and mentor, Albrecht Haushofer. Haushofer was one of the plotters of the unsuccessful July 20, 1944, conspiracy to assassinate Hitler. He was captured and executed for his part in the abortive attempt.

A look of sadness clouds Dr. Hilderbrandt's eyes as he recalls the events leading up to his friends' death, events that were critical in shaping his own life. "It helps me to feel myself closer to them doing his work."

Do Dr. Hilderbrandt and members of Actiongroup August 13 actually assist people in the East to escape? There is a long pause. Perhaps the Herr Doctor would prefer not to answer.

"No, I will answer. . . . In our work we cannot do such a thing. One must say conspiracy has nothing to do with informative work." The doctor seems somewhat chagrined at the question. "There comes so many people to us," he continues, "who have problems for escaping. . . many, many people. They need our confidence. They have a relative in the East. . . . We never ask for their names or any details. We don't want to know."

But Actiongroup August 13, whose membership includes many refugees and former border guards from the East, can (and does) give advice.

"We can only warn these people not to get into the hands of the escape-helpers. There are people who are not responsible and who make great financial gain. There are many who make only money, they ask for money even before they do nothing. We know their names.

"We can say to the people who come to us for advice, and this is very important," Dr. Hilderbrandt emphasizes, "if you go to escape-helpers, deal only with people who do not take money before, and make it only with people after you put at least 40 to 50 questions to them, for there are many secret agents of the East here in West Berlin.

"We say also to these people, if you make your own ideas of escape, the risk is not greater. For example, if relatives help relatives, Germans helping Germans, you know.If they go over the Eastern countries and are arrested, say, in Bulgaria, or even in Romania, what can happen to them?For escape-helpers, not very much. They are Western citizens, German citizens. They get three, four, or five months.No more."

What happens to the would-be escapees? "They get more," Dr. Hilderbrandt conceded. "But they get not so much if they are relatives. They do not get punished for dealing with people against the state for money. That is what they do get for dealing with professional escape-helpers."

Are there legitimate escape-helpers inWest Germany? "I think practically no. We know about 20 escape-helpers by name, but they make it only for great money. They are not reliable."

The usual price the escape-helpers ask to bring people out of Eastern-bloc countries is now about 20,000 marks for one person. But this price, Dr. Hilderbrandt cautions, can rise to 25,000 or 30,000 marks ($10,500 to $12,600).

In 1960, nearly 200,000 refugees fled from the eastern zone into the West -- most of them Germans. A year later, despite the erection of the wall, about 207 ,000 managed to escape from the German Democratic Republic. But in 1962 that figure dwindled to 21,000, and then, for the next two years, climbed to about 42 ,000 each year.

Recently there has been little news about daring escapes from the East. Is security that much tighter or are conditions improving in communist East Germany?

"I think," Dr. hilderbrandt says, "that this also has to do with our work, because we made the people of East Germany know how great is the danger, and that of all escapes attempts only every second or third is realized."

He estimates that there are about 5,000 political prisoners in East Germany, about 65 percent of them captured trying to escape.

"Every year the West German government tries to buy some of these people out. Mostly the ones who have served at least two-thirds of their sentences. In 10 years we have bought out about 10,000 of these prisoners."

When was the last time someone from the East made good an escape? The newspapers rarely publish such stories today. The director of the museum smiles. The tone of his voice indicates that the question is naive.

"Practically every day," he replies with some pride. "You must know that in 1980 -- we just put out the figures -- 3,700 refugees came into West Germany or West Berlin from the East."

Today the successful escapers get out more by bluff than by bluster. The days of crashing a bus into the wall, blowing a hole in the wall, tunneling under the wall, or flying over the wall are past.

"The physical hindrances are so fundamental, so strong," Dr. hilderbrandt explains, "that only silly people would atempt it. We talk to escaped border guards (one is a trustee of the museum) and they tell us that perhaps in the last year only one or two people got as far as the last hindrances. Most are arrested 5,000 meters [16,500 feet] from the border."

Yet the contraptions on display at the museum are the marvels: The minisubmarine (powered by a tiny motor meant only to drive a lightweight bicycle) was powerful enough in 1968 to propel an East German under the Baltic Sea to Denmark.

The famous Isetta automobile, which looks hardly big enough to accommodate a driver with wide elbows, had been so altered that two "passengers" could be brought out of East Berlin on a single venture. In all, the car on display made 18 successful escape trips before it was retired. The escapees were stowed into the discarded heating system and battery compartments.

Dr. Hilderbrandt is especially proud of the hot-air balloon in which a family escaped to the West. The story, which made world headlines, caught the free world's imagination. An American millonaire offered to buy the balloon from the escapers for $100,000. The Balloon Museum of Great Britain also bid on it. But it ended up here at the House at Checkpoint Charlie.

"We told the balloon escapers that we could not give them money," Rainer Hilderbrandt says. "We can give them only the honor to give it at the place where most people can see it, and where it is also explained to people who come to the museum from both East and West."

Near the museum is one of prewar Berlin's most popular centers, Potsdamer Platz. Today it is a barren patch with a few shops where tour buses stop to permit tourists to climb the gallows-like structure in order to peer over the wall at a bleak landscape dictated and designed by the Soviet Union.

From the top of the railed platform, almost as far as the eye can see, stretches a no man's land of are lights, sentry towers, antipersonnel and antivehicle obstacles bristling with barbed wire.Beyond, buildings, some still shabby 36 years after the last shot was fired in Berlin, look like a cardboard movie-set.

The foreground is dominated by the off-white concrete blocks that make up this part of the wall, a magnet for graffiti lovers. On this day, as always, the surface of the wall is occupied with pent-up bitterness, the shame and, yes, even the wit that West Berliners vent on the communist neighbors. It is standard wall-fare that wall-watchers have come to expect, even enjoy.

Down near the dirt someone small in stature had scrawled in chalk, in English:

"When I Die I'll go to Heaven Because I've Been Living in Hell."

The House at Checkpoint Charlie, No. 44 Friedrichstrasse, is open daily, 9 a.m. to 8 p.m. Admission for adults is 2 marks (80 cents). A special half-admission rate for children and individuals traveling with a group is available. Visitors from Eastern-bloc countries are admitted free of charge.m