American Security Corp should offer a short course for the region's bankers on how properly to prepare an annual report. And most of its competitors should sign up.

Of course, antitrust statutes probably would prevent such a gathering. But the end result might be a better-informed investign public and and general public. As economic issues become more complex and controversial, that's the type of collusion we need

In the absence of any requirement by federal bank regulators that disclosure of business transactions and banking activites be explained as comprehensively as possible, virtually all banks follow the letter of the law and disclose to their owners -- and thereby the overall public -- only those bits of information specifically mandated.

But a few institutions - notably BankAmerica Corp. of San Francisco, owner of the world's largest bank, and several New York-based bank holding companies - have shown that they recognize a new spirit in the land that calls for more candor. Investors want answers to tough questions about their companies. The genera l public is aware of soaring bank profits and interest rates on their loans and therefore expects a credible accounting from financial institutions that long have sought to survive on a simple relationship of trust between banker and customer.

More than at any other area financial institution, American Security Corp. executives apparently have come to believe that trust alone no longer can suffice.

Thus, the parent company of Washington's second-biggest bank has published a 50-page document that tells a lot more about its operations last year than any other bank firm in the region reveals. American Security began its effort to broaden annual-report disclosures two years ago and has made steady improvements.

"In creating this new format for corporate disclosure, we have invested a great deal of time and effort." We could not have attempted to pioneer in this area, however, without the cooperation an encouragement of the Securities and Exchange Commission," said American Security Chairman Carleton Stewart.

"As financial reporting requirements become more complex, it is necessary for companies to try to present their data in such a way that it makes sense to the average stockholder," he added.

Among the unusual features of the American Security report is inclusion of an annual statement required of all companies under SEC jurisdiction, called Form 10-K, which forces firms to detail specific financial data as well as all material factors affecting business. National banks file similar documents with the comptroller of the currency.

Even though these documents are on file in public record rooms, most investors do not see them and most companies do not go out of their way to seek widespread dissemination -- often because of potentially embarrassing information that does not get into the bland annual reports sent to stockholders.

American Security has taken a further step, moreover, by converting much of the tabular material required in an SEC 10-K to 23 color charts and graphs. This was a particularly - time - consuming process for the bank company's accountants.

Finally, this year's report includes for the first time a section called "How to Use This Report," a simple guide that includes definitions of such financial terms as "net interest margin," "net interest spread" and "pre-tax equivalent."

Among the types of information most investors don't get, American Security disclosed that in 1978:

The 10 largest holdings in the company's investment portfolio were tax - exempt securities of states, led by Pennsylvania ($12.4 million), Maryland ($11.7 million) and Oregon ($11.2 million). State and political subdivision issues accounted for 60 percent of an overall portfolio of $337 million.

Trust department assets under management at year's end were $2.1 billion, with increased investments in the utility, health care, bank and financial services industries. Listed are the 10 largest stock sales and acquisitions during the year as well as the 25 largest stock holdings. Unloaded last year were large blocs of Beckton Dickinson (in the controversial Sun Co. takeover), Whirlpool, Philip Morris and 3M Co. Major purchases included Raytheon, PepsiCo, Bristol Myers, Denny's and Time Inc.

Peat, Marwick, Mitchell & Co. has been hired to replace Price Waterhouse Co. as principal accountants for 1979, following a recommendation by the board's audit committee that "was not based upon dissatisfaction... with Price Waterhouse."