Government workers and others who were outside the old Post Office Building tower at 12th Street and Pennsylvania Avenue NW around 12:30 p.m. yesterday were treated to a rare pealing of the tower's bells. They're normally rung only on national holidays and special occasions.

Yesterday's special occasion? It was the visit to the tower of its half millionth visitor and his family, a wife and two sons.

As a National Park Service ranger voiced it, the man introduced moments later was from what sounded like "Charles Town, West Virginia," but a voice from the honored visitor's tour group called out, "Charleston, West Virginia -- not Charles Town, Charleston." Confusingly, the state has both.

No. 500,000 to the tower, opened for public visitation on May 2, 1984, turned out to be Bernard Casdorph, 35, of Elkview, W. Va., a Charleston suburb, and a manager of a supermarket produce department.

Somehow, in reaching the tower via a crammed elevator, he got separated from his wife, Sandra, and his sons, Krisopher, 7, and Jared, 3, who were still waiting for the elevator after debarking from the tour buses. "They're down-stayers," he explained twangily.

When his family finally arrived, it was showered by gifts -- a luncheon voucher, among other things, from the Pavilion, which has restaurants and shops on the 86-year-old building's lower floors, and a pass on Tourmobile sightseeing buses. And the visitors were welcomed by William F. Madison, regional administrator for the General Services Administration, which renovated and manages the building, and by Robert Stanton, deputy regional director of the National Park Service, which controls and staffs the sightseeing tower.

Arriving at the building, Casdorph said he got wind that Visitor No. 500,000 would be chosen. "I just didn't think it'd happen to us," he said.

It was in his honor that a team from the Washington Ringing Society showed up to pull the ropes that ring the building's carillon, a Bicentennial gift from Great Britain to this former colony.

The team was led by John King, normally the captain of the bell ringers at National Cathedral. He was brought in to captain the team in place of the man who usually heads the ringers at the old Post Office towers, but was out of town. So it can be said accurately that they brought in a ringer ringer.

If yesterday's event proves one thing, it's that, in an administration that is exceedingly conscious of political screening for media events, nobody in the welcoming party thought to wonder about possible partisanship of the tour group.

Winner Casdorph's group, 86 people in two buses, was arranged -- with motivations that can be assumed to be not apolitical -- by Rep. Robert E. Wise (D-W.Va.). To repeat, that's Democrat of West Virginia.