The Old Post Office Building, whose Romanesque charms will soon be unveiled in renovation, received a tardy bicentennial gift of bells yesterday thanks to Anglo-American friendship, World War II and a certain amount of British horse manure.

The bells--actually a 10-bell peal, as they say--were given to the United States by the Ditchley Foundation of Great Britain in gratitude for this country's assistance to the Mother Country between 1939 and 1945. Presentation of the 1976 gift was delayed until there was a suitable place to hang them.

They were installed yesterday in the building's previously bell-less bell tower under the watchful eye of William Theobald, 68, of the Whitechapel Bell Foundry in London. Theobald, like his firm, tends to view jobs of this sort through a somewhat longer lens than his American counterparts.

"You can't really call it a permanent installation," he sighed. "After 150 years we will have to rotate the bells about a quarter turn" on their vertical axis to even the wear from the clapper. "Another 80 years and they'll need another eighth of a turn."

That Theobald won't be around to do the work is hardly the point. He expects Whitechapel will, since the firm cast its first bells in 1570 and only "moved to the new place" on London's Whitechapel Road in 1728.

Besides, you can't be too careful with maintenance. The Liberty Bell, a Whitechapel casting, is a case in point.

"You broke it, we didn't," Theobald said. "Now you might ask why we didn't send a new one over if the old one broke, and actually we did. But you never installed it. Preferred the old one with the crack."

The Post Office bells, ranging roughly from two feet to 4 1/2 feet in diameter and in weight from 300 to 3,000 pounds, are designed to be similar in tone and pitch to the Whitechapel bells rung in Westminster Abbey since 1596.

Sometime during the week before the April 19 dedication of the renovated post office, Theobald will ring them to see. He is a founding member of the North American Guild of Change Ringers, a sort of Who's Who of tintinnabulators. He's been pulling bell ropes at various cathedrals for half a century in his off hours, and actually it was the ringing that got him into bells, rather than vice versa as you might think.

The stepson of a coal stoker on the Cunard Lines (his father was killed in the Ypres offensive of 1917) he "rung my first peal on my 18th birthday" at Portsmouth Cathedral while an apprentice metal worker at the Vickers Armstrong Aircraft Co. He became intrigued with change ringing--the orchestrated sounding of large ranks of bells in precise order--but soon found himself making wings for Spitfires 18 hours a day, seven days a week, under the shattering bombardment of Hitler's Luftwaffe.

Even had he had the time, there was nothing to ring anyway: bells were reserved by law in England in the early war years to sound the alarm of a Nazi invasion.

But in the postwar years the lure of the bells pulled him to Whitechapel where 30 employes maintain a craft whose secrets were first documented by a German monk named Theophilus ("similar name, no connection," Theobald says) in the 12th century.

The Post Office bells are 78 percent copper and 22 percent tin. They were cast in a mold made of a time-tested mixture of London clay, cow's hair and horse manure.

"The horse manure is most important," said Theobald. "The clay gives the mold the form and the cow's hair binds it together. The manure generates gas as the mold bakes, and the fine hairs in it burn away in the process making the mold both strong and porous"--a critical factor in the casting.

Each Post Office bell carries the Great Seals of the United States and Britannia as well as a relief of the flower "London Pride." The Ditchley Foundation, which underwrites conferences and other efforts to strengthen Anglo-American ties, hopes they will be rung on special occasions when "a great peal of bells . . . can provide that occasional . . . inspiration which helps to drive civilization on its way."

Theobald will be off soon to reframe the Whitechapel bells in Boston's Old North Church--the same ones that once warned Paul Revere that the British were coming. He said those now in the Post Office would have been here sooner but the ship due to bring them was diverted by the Falklands crisis.

With bells, it seems, one is never far from history.