Old-line Washingtonians remember when some moderately affluent people lived in apartments above the stores that were part of the downtown. Only a few of those dwellings-over-the-stores remain here.

But the pendulum may be taking another swing in the direction downtown living over commercial space. Next spring a new office building at 2501 M St. NW will have three stories of upper-price condominiums over five floors of office space.

Located in the reviving West End section, the 2501 M building will have 20 two-bedroom duplexes, two one-bedroom duplexes, 12 one-bedroom units and four efficiencies. Prices range from $92,500 to $232,500.

Two years ago the nearby West-bridge condomonium apartment, located next to and connecting with an office building, was sold out quickly. $ burr, Morris & Padoe, which is handling the selling of the condo apartments for developer-builder Melvin Lenkin and his partners, reported it had nine sales contracts for apartments, which will have a private entrance, a posh lobby and a skylit foyer. Each dwelling will have a six-foot whirlpool tub in a marble bathroom.

The building may spark other mixed-use (commercial-residential) buildings in midtown areas where zoning is amenable to it.

Buildings such as 2501 M, which was designed by architect Vlastimil Koubek, may encourage Lenkin and other developers to do more of the same.