Leo M. Bernstein's official biographies do not include any mention of a theatrical career during his nearly 50 years in the banking, real estate and savings and loan business in Washington.

But he loves to perform, and a luncheon here yesterday for local newspaper reporters was vintage Bernstein.

In terms of Bernstein's current principal business venture, as chairman and controlling owner of the former Diplomat National Bank since July 25, he said he has been having a lot of "fun." Obviously pleased with what has happened in the last nine months, Bernstein had a batch of important pieces of information to relay:

As of 11 a.m. yesterday, the bank got a new name -- Washington Bank, N.A. (national association, regulatory terminology for a national bank). Federal bank officials approved the change in name, even though some existing Washington banks protested that too many banks would have similiar-sounding names.

As of March 31, the bank recorded its first quarterly profits in a dismal history that began in 1975, when Diplomat was chartered as a bank to serve Washington's Asian-American community. The earnings were $85,000 (14 cents a share), compared with a loss last year of $435,000.

Suffering from bad loans, government probes and questions about whether Korean interests really owned the bank, Diplomat hit the government's list of troubled banks until bids for ownership

Washington Bank was written off its books all previous loans unacceptable under current bank standards (a total of more than $500,000). Otherwise, business has expanded sharply, with assets up 70 percent since July 31 to $16 million, deposits up 64 percent to $13.6 million and loan volume up 95 percent to $10.45 million.

Maj. Gen. Kenneth J. Hodson, a retired judge advocated general of the Army, has been elected vice chairman of the institution. The bank's board also has been expanded by the addition of several area business persons.

Bernstein tried to read these announcements from a prepared statement but couldn't help interjecting from time to time his own interpretation of what was happening, not only to his newly christened bank but also throughout the financial industry generally. He complained about the "fierce competition" from growing money market mutual funds and expressed worries about the savings and loan industry.

Asked if he ever thought about a merger of his new bank with Guardian Federal Savings and Loan Association (which he founded in 1948 and of which he was president until 1967), Bernstein's reply was: "Every night." While such financial institution combinations are illegal under current laws, Bernstein is among a large number of bankers who expect the current financial revolution to lead to such consolidations.

And then, in the next breath, he was talking about one of his favorite subjects: the history of Washington. A major collector of Washingtoniana over the years, Bernstein noted in passing that his bank will start using a bust of George Washington as part of its identification.

He revealed that his Washington City Museum -- books, maps, prints, letters and documents from early American presidents and a lock of George Washington's hair (the color was red, according to Bernstein) -- will be housed at the Washington Bank office on K Street NW. To make room for the display, bank operations will be moved to a separate office building.

"The new name identifies the bank with the historical significance of the nation's capital," said Bernstein, and the addition of his historical collection will bring under one roof some specific reminders of the past.

Bernstein, who, after his S&L experience, went on to revive the financially troubled D.C. National Bank starting in the 1960s, said he wants Washington Bank to concentrate on serving the business, professional and association communities.

Within five years, he predicted, area banks would be permitted to share automatic teller machines, which could become as common as mailboxes are today. Customers in the future will need only access to such machines plus a "personal" banker who is interested in the customer's needs, he added.

Washington Bank assets would double by the end of 1981 under the ambitious growth plan outlined by Bernstein yesterday. Advertising and marketing will now begin ("I was waiting to change the name. . . . Not a single promotion letter has gone out yet," he said).

And where will Washington Bank be in a decade? Bernstein said he expects only about five big banks to survive and indicated that his institution might well become one of several institutions in a regional bank holding company.

As for the 40,000 Asian-American residents in the area, Bernstein noted that many are still customers and that several leaders remain on the board or have been added to it. He vowed to serve the entire Washington community.