For residents of historic Alexandria, the past is much more than a prologue and for realty agents there, the traditional benchmarks of property value - location, location, location - are often supplanted by three other criteria - age, age, age.

It is not surprising then that an oval-shaped plaque certifying hundreds of homes in the riverside city as genuinely old and of historical and architectural significance, is considered by many homeowners as a mark of prestige as well as a tangible real estate drawing card.

More than 560 of the plaque have been issued by the private Historic Alexandria Foundation since 1965. Originally, only the 897 buildings on the "Early Buildings List" drawn up by the foundation were eligible to receive plaques.

Most of the buildings on this list were constructed prior to 1846 with a few dated as late as the 1870s. The majority of the buildings are located in the city's central "Old and Historic Alexandria District."

As part of an expanded preservation effort, the foundation recently decided to extend eligibility for the plaques to homes built as recently as 100 years ago no matter where they are located within the city.

The plaques will now be given to "much younger homes," said Marianne Hulfish, who lives in a 1787 "plaqued home."

Twelve years ago, the 10-inch-high plaques were aluminium and cost the homeowner $10. Today, they are made of bronze and cost $65, according to William Warwick, a trustee of the foundation. Each building on the "Early Buildings List" has a registry number that is inscribed on a brass plate in the middle of the plaque.

Realty agents seem to agree that the presence of a plaque adds to the value of a home. "Given the same location and same configuration (of two homes) the value (of one home) can be as much as $10,000 higher if it's plaqued," said one agent. "In run-of-the-mill plaqued homes," the oval cachet means "at least $1,000 (in added value)," he said.

The certified seal of age often convinces home buyers to overlook defects like floors sloped at 45 degrees where "I'd swear you'd roll out of bed!" according to another real estate agent.

The news that homes as new as 100 years old are now eligible to receive plaques delighted one real estate dealer. "Now I can go out and have my home plaqued," she said gleefully.

Real estate ads for Alexandria properties often mention the plaque as an added attraction and agents report that people inquiring about ads often ask if the home has a plaque.

Warwick believes there will be a rush to get plaques when the news spreads that 100-year-old homes are now eligible since many people "have been hankering after a plaque for 12 years." Why? "For the same reason, I guess, one hankers after a Cadillac or a yacht - it's a status symbol," Warwick said.

Hulfish said her family was "delighted" that their 190-year-old home was now entitled to a plaque but they don't view it as a status symbol like many of the people now moving into Alexandria.

Hulfish's family has been in Alexandria for five generations and they "take it for granted," she explained.

Several homeowners said plaques were already hanging on their homes when they purchased them. Robert Pringle, whose 1794 to town house is a stone's throw from the Potomac River, doesn't even know how the plaque got on his building. It might have been placed there by one of the tenants, he said.

Pringle, who said he "once overheard a song and a dance about how (the plaque) made the home a genuine antique and would increase the value by $35,000," does not appear too impressed with his plaque. "It's a lot of nonsense but it does add to the value of the home," he said.

And yet, Pringle notes, newly built town homes right down the street "are selling for $35,000 more than my home."

Mary Elizabeth Recker, whose house dates from the 1850s said she "didn't really know why" she and her husband bought a plaque except that they "wanted to help the foundation and everybody else was doing it - maybe we did it just to keep up with the Joneses," she added.

The foundations decision to broaden the eligibility for its plaques comes in conjunction with recent measures by the City Council aimed at preserving a greater number of buildings throughout the 228-year-old city.

According to foundation chairman Jean Keith, residents in Alexandria were shocked when the owner of an 1854 Greek Revival-style town house at the corner of South Washington and Franklin Streets tore down the building in 1974.

The destruction of that building, popularly named "The Shadows," galvanized the community to strengthen the laws forbidding demolition of historically important properties, Keith said.

Although "The Shadows" was within the city's protected historic district, it could not legally be saved from demolition by its owner because it was built after 1846 - an arbitrary cut-off date set up when the historic district was created in 1946.

Keith said he and other members of the foundation pointed out to city officials about 200 other buildings that were vulnerable to demolition either because they lay outside the historic district or they were built after 1846.

As a result, the City Council enacted legislation in 1975 that put all buildings within the historic district under the protective wing of the city's Architectural Review Board as they become 100 years old.

This year the Council extended that protection to all buildings that reach 100 years of age anywhere in the city Buildings falling under the domain of the board cannot be demolished or have their exteriors remodeled without prior approval of the board.

In addition, the city created a "historic properties coordinator" last year, gave him a budget of $19,000 and told him to do a survey of all the homes 100 years old and older outside the historic district.

Richard Bierce, the first historic properties coordinator, said his office has taken over researching the property titles of homes to determine if they are old enough to receive one of the foundation's plaques.

So far his office has gotten about a dozen such requests from city residents but has not yet completed research on any of them. Researching a title can take anywhere from one hour to three days, depending on how well it is recorded, Bierce said.

Affixed next to the front door of an Alexandria home, the plaques are neither a legal nor a magic deterrent to demolition. They are primarily "a psychological barrier," said Keith, "so it will be harder, psychologically, to tear a building down."

Most people who work to stave off the destruction of old buildings in Alexandria do it, as one observer out it, for the "born love" of the city, but Keith noted that there are other important considerations in keeping historic buildings intact.

"I think most people in this city realize how much money comes into it from (tourism in) the historic area. This is big business," he said.