Atmosphere: Genteel and refined but very warm.

Hours: Dinner seating between 5 p.m. and 8 p.m. Doors close at 8. Closed Sunday and Monday.

Price range: $3.75 to $12.75.

Credit cards: MasterCard, Visa.

Reservations: Not taken. First-come, first-served.

Special facilities: Steps would be difficult for handicapped. Parking on street.

If you are in Baltimore with your kids visiting the McCormick Spice Factory, the U.S.S. Constitution, the new aquarium, or the Walters Art Gallery, you might want to end the day with an early dinner at Marconi's.

Established 62 years ago, Marconi's is authentic old Baltimore (pronounced Bawlmer). It remains a pleasing and somewhat eccentric relic of another era. The food mirrors the authentic flavor of the setting, and also a bit of its eccentricity.

The restaurant is in a grand old town house built in the middle of the last century. You enter on worn white marble steps that are a Baltimore trademark. It's first-come, first-served--no reservations. Doors open at 5 p.m. and close at 8 p.m.

Inside, people waiting to be seated lean against the walls of a plain, long, narrow passageway typical of the railroad flat floor plan of the 19th century. It's unusual to find a restaurant that does not ply captive customers with drinks before dinner; Marconi's is too refined for that.

Every so often the maitre d' parts the hallway crowd to reach into an open glass cabinet which incongruously holds bottles of wine and assorted candy bars.

Some recent housekeeping--new wallpaper, a fresh coat of paint--has reduced the slightly seedy air that characterized Marconi's for years.

The small dining rooms are like snapshots of the past: high ceilings with huge windows, massive crystal chandeliers fully lit (Marconi's hasn't succumbed to candelit "atmosphere"), tables far enough apart so you don't feel cramped, starched white napkins on the tables with good though worn silver and ancient glass water carafes.

The menu is an eclectic combination of French dishes such as vichyssoise and sweetbreads Bordelaise, Italian standards such as minestrone, veal scallopine and spaghetti, and home-style Maryland specialities such as shad roe with bacon, fresh broiled rockfish and oysters sauteed with ham.

Soups make the best appetizers. The vichyssoise is thick and creamy, though weak in potato flavor; minestrone is dense and hearty beef and vegetable soup not the least Italian in flavor, but good (each 85 cents).

Fish dishes mostly come off well. Rockfish ($9) was fresh and sweet, the broiled portion huge yet moist. Shad roe ($9) is always good at Marconi's. Excellent thick-sliced smoky ham garnishes a number of dishes well, including oysters ($9).

Veal dishes appeared to be popular. Lamb chops, broiled, are a bargain: six crisp ribs for $9.75.

Shrimp dishes generally are overpriced, considering that the shrimp are neither large nor fresh, though portions are generous. French fries and cottage fries are particularly good, made to order from scratch.

Regulars know to order the creamed spinach, a smooth, delicious nutmeggy concoction, and the fried eggplant, large chunks in thick batter, quickly deep-fried and crunchy.

An oddity is the house salad ($2.25 for a bowl that serves two), produced by our waiter at tableside with much dramatic chopping and mixing, the result being simply iceberg lettuce, chopped hardboiled egg, some canned pimento and anchovy in a thin, mild mayonnaise dressing, all of which seemed anticlimactic.

Desserts ($1.25 to $1.75) center around seasonal fruit. Right now lovely large strawberries garnish meringue, ice creams of good quality and cheesecake.

Service is charming though pokey, so expect to wait a bit between courses. Children are welcome and treated extremely warmly by the staff.