Last Thursday evening, Graziella Teresa Corrocher walked to the window of her fourth floor office at Banco Ambrosiano headquarters in Milan and dropped quietly to her death in the courtyard below.

Clearly distraught over the mysterious disappearance a week earlier of her boss, controversial Italian banker-financier Roberto Calvi, she left behind a note, scrawled in bright red ink, damning him for running away and "for all the damage done to all of us at the bank of whose image we once we so proud."

Less than a day later, Calvi was dead, his body found hanging by the neck from Blackfriars Bridge across the River Thames in London. His pockets reportedly held several thousand dollars worth of foreign currency, a false passport with a visa for Brazil, an airline ticket to Rio de Janeiro and more than 20 pounds of pieces of cement. The results of an autopsy, expected to be released in London Tuesday, are likely to shed light on whether the 61-year-old Calvi was murdered or committed suicide.

His disappearance on June 10 from his Rome apartment, followed by his death, have sent shock waves and deep concern throughout the Italian financial world and threatened the future of Italy's largest private bank, with $20 billion in assets. The Milan bourse, which has since partially recovered, reacted to Calvi's disappearance with a flurry of panic selling. Last week a 30 percent drop in the bank's share price led stock exchange authorities here to suspend trading. Today Italy's central bank, the Bank of Italy, announced the appointment of three special commissioners as administrators of Banco Ambrosiano, with all the powers formerly vested in the bank's board of directors, which resigned late last week.

The appointment of the commissioners was designed "to safeguard the interests of depositors and to guarantee the regular administration of the bank's affairs," the Bank of Italy said.

Calvi, a self-made financier who started at Banco Ambrosiano in 1947 as a clerk and rocketed to the apex of the Italian financial world, long had been under a shadow here, partly because of his past association with Sicilian financier Michele Sindona, and partly because of his reputation as a highly secretive wheeler-dealer.

Then last spring his name turned up on a mysterious list of 953 persons supposedly belonging to a secret Masonic lodge. Later he was charged and convicted of offenses involving the illegal export to Switzerland of about $27 million.

He was sentenced to four years in prison, released from jail after attempting suicide and was due to face an appeals court this week.

Since his release from jail, Calvi had returned to his previous life style of 14-hour work days and few public appearances.

The crisis leading to Calvi's disappearance and, perhaps, also to his death is primarily a matter of conjecture. Shortly before his disappearance, the Bank of Italy allegedly had written to Calvi, suggesting that the bank had a credit overexposure of about $1.4 billion.

Italian banking authorities appear to believe that the bank's Italian operations are basically sound. Its properties include a thriving regional bank in northeastern Italy, an insurance group, leasing and real estate.

But a series of foreign subsidiaries, particularly in Latin America and the Caribbean, are believed to be considerably more suspect.

Banking sources here believe that Calvi may have used these subsidiaries to secretly assure his own near-absolute control of Banco Ambrosiano.

Another factor heightening the scandal in Italy is that Calvi is believed to have been linked closely to the Vatican bank headed by Archbishop Paul Marcinkus, the IOR, the initials in Italian for Institute for Religious Works.

Officially, the IOR owns only 1.58 percent of Banco Ambrosiano, but it also has an interest in other Ambrosiano subsidiaries.

Today, the Rome financial weekly, Il Mondo, speculated that the Ambrosiano "crack" could have been caused by the Vatican bank's refusal to honor letters of guarantee covering debts by various Ambrosiano subsidiaries.

The Bank of Italy investigation into the Banco Ambrosiano group's tangled affairs is expected to take at least a year, but investigators here hope that details of Calvi's movements in London before his death may provide some helpful clues.