When Ferdinand and Imelda Marcos sent the message "Happy Birthday" to Markus Geel in Zurich, it didn't mean Monsieur Geel was a year older.

That greeting, according to documents served on Marcos here this week by the Philippine government, meant the Marcoses wanted money from their secret trust, the "Sandy Foundation," set up for them and their children in Vaduz, Liechtenstein.

Whenever Geel got the birthday greeting, he was to contact Ralph Klein, his representative in Hong Kong, the documents indicate. Then Klein was to travel to Manila to meet with the Marcoses and handle the matter.

Through such clandestine devices, codes and false names, the Marcoses funneled hundreds of millions of dollars into and out of foreign bank accounts, according to the documents served on the ousted leader by the Philippine Commission on Good Government, which is investigating Marcos' wealth.

Estimates of the holdings of Marcos, his wife and close associates in Swiss banks range from $1 billion to $5 billion, but even lawyers representing the new Philippine government of Corazon Aquino do not know the exact amount, according to Jovito R. Salonga, chairman of the commission.

The acounts have been frozen by Swiss authorities since March 25.

Marcos, when asked about the documents, said in a statement released by an aide at his exile home in Honolulu that the amounts and ownership of the accounts, as well as the authenticity of the documents, were all "under question" in "secret hearings" in Swiss courts.

Marcos said leaks of the documents were part of a campaign of "mud slinging" and "black propaganda" by Philippine officials who "want to sensationalize and to bring to public trial those who oppose and question" the Aquino government.

Copies of the documents were presented to Marcos as part of a Philippine investigation into his alleged "hidden wealth." Copies were also obtained by the Honolulu Advertiser.

The documents indicate that if the Marcoses wanted money out of secret accounts opened with the Swiss Credit Bank beginning in 1968, they would use the pseudonyms "William Saunders" and "Jane Ryan."

The documents include a copy of a note on presidential stationery at Malacanang Palace in Manila on which someone repeatedly practiced the signature of "William Saunders."

There was a more elaborate code to assure that Marcos' communications with the Swiss bank were authentic, the documents indicate. The first cable was to be numbered "one" followed by the word "sugar." Successive cables, numbered in order, were to begin with the words "copra," "plywood," "copper," "chromite" and "nickel," in rotation.

In addition, the name of the sender of the cable would have to change every two months. If it was July or August, for example, the sender's name would be "Andrew Warner."

The papers included contracts, trust agreements, analyses, receipts, instructions and other financial records involving institutions in the United States, Hong Kong, the Caribbean and Europe.

They were found hours after Marcos and his entourage fled Malacanang Palace in the face of a military rebellion, according to Potenciano A. Roque, who said in an affidavit accompanying the documents that he was sent to the palace by Aquino.

At about 2 a.m. Feb. 26, four hours after Marcos fled, Roque said he was brought to Marcos' presidential living quarters by military personnel and was left in charge of the palace.

"I then entered the presidential bedroom, and upon entering found a file safe located near the doorway," Roque said in the affidavit. He said he found the combination to the safe posted inside a door.

"I proceeded to open the safe and found sheafs of documents which, upon closer inspection, turned out to be documents regarding Mr. Marcos' papers and bank accounts with Swiss banks, some papers regarding an Netherlands Antilles corporation, and other papers referring to various financial transactions."

Roque said he put the papers in the safe and kept them there until he turned them over to Salonga.

On Tuesday, Salonga told reporters in Manila that millions of dollars in the Swiss accounts may be returned to the Philippine government "in a matter of months," due to "a number of developments which cannot be fully revealed as yet.

"There is proof that this is the product of illegal activities. We have proof to show that this comes, for example, from war reparation payments, from commissions on highway and public works projects," Salonga said.

Marcos consistently has refused to discuss details of his overseas accounts but has denied any wrongdoing.