American Security Bank inaugurated a new era of supermarket retail banking in metropolitan Washington yesterday with the formal opening of its 31st office at 4834 MacArthur Blvd. NW.

Taking his cue from the Safeway store across the street, American Security Chairman Carleton M. Stewart wheeled a shopping cart down the tiny "aisle" of his newest branch, eyeing selections from such offerings as certificates of deposit and auto loans.

"We're merchants," Stewart said, adding that this new approach to selling bank services had "caused a lot of stomach-churning" at American Security, the second largest of Washington's banks in terms of deposits.

Bankers have been at faults in the past "for somewhat misleading the public" with such promises as free checking, the bank officer added. Nothing is free, and the challenge facing bankers today is to provide the services the public wants at a cost that still permits bank profitability, he continued.

With the relatively small branch on MacArthur Boulevard, which Stewart described as "a model" and an "experimental laboratory," American Security hopes to conduct the sort of market research with its customers that soap manufacturers conduct in the Safeway.

If a concept works, it will be spread throughout the bank's branching system. If something fails, it will be dropped.

Borrowing marketing concepts from Safeway and other food chains, American Security will promote its various offerings with huge signs on its outside windows, a sign in its lobby highlighting this week's "specials," and wall signs that display current rates for various types of loans and savings.

"As retailers, we want to be responsive to our customers in terms of what we offer and how we deliver it.We want to bring our inventory out into the open, and allow customers to examine the products and make an informed choice," Stewart stated.

For example, one new service being tested at the MacArthur Boulevard branch is a Visa checking account, by which a customer will be issued a Visa card that may be used to buy merchandise at any merchant honoring the bank card.

However, American Security will not issue Visa as a credit card. Rather, the Visa cards will be tied to the bank's overdraft checking account; customers who charge goods or services with their Visa card will have the transaction debited on their checking account.

Stewart left little doubt that American Security plans to offer Visa debit cards throughout its system once any "bugs are eliminated - thus becoming the first bank in the District of Columbia to offer national bank credit cards.

American Security also plans a rapid expansion of its branches throughout the city, possibly adding five offices in the next year, including two on Upper Wisconsin Avenue NW, one on Upper Connecticut Avenue NW and one at the Washington Hospital Center.

In an era when bank officers have been hestitant to open new branches because of the cost, Stewart said yesterday that his bank is "trying to lead an attitude change." Although the marbel, furniture and other fixtures make a regular bank branch cost about $350,000, facilities modeled on the MacArthur Boulevard branch will cost less than $70,000 to open, Stewart said.

For example, each teller position consists of a modular unit so new positions can be installed or removed virtually overnight. Modular units can be stored in warehouse and moved about on demand.

A new International business Machines Corp. automatic teller machine - the bank's first - has been installed next to the human tellers; if there's a line at the windows, customers can move over to the machine for most transactions.

Stewart said American Security also will install an automatic teller machine in the branch vestibule to test consumer reaction. A door to the vestibule could be opened by use of a plastic bank card - thus permitting access to the machine itself.

To promote the new branch, American Security mailed brochures to area residents.

Although the new branch offers all services, some normal activities of a branch will not be conducted at the MacArthur Boulevard site. For example, no letters will be typed by bank personnel there. The branch is a "satellite" of a branch in Georgetown, which will supply the smaller office with some services.

A similar establishment of regional and satellite branches throughout the city is being planned. Stewart also said studies now being made on possible branches in the suburbs - to offer services legally possible under branching laws - will be completed shortly.

The new branch will be open from 9 a.m. to 3 p.m., except on Thursday, when the bank will stay open until 7 p.m. That's the heavy shopping night across the street at Safeway, Stewart noted.