Open for lunch 11 a.m. to 2:30 p.m. weekdays, and for dinner 5 to 10:30 p.m. Monday through Saturday. AE, CB, BA. Free parking for dinner.

Food: Accessories make the meal

Style: Yesterday's elegance and pace

Price: Moderate at lunch, slightly higher at dinner.

Not all Washington restaurants come and go faster than the Yellow Pages can mark their passage. Some have even been around for decades. Thirty years ago you could have eaten in Sholl's or Reeves, in Martin's Tavern, Arbaugh's Napoleon's. You could have had seafood at O'Donnell's Harvey's or Hogate's, though not necessarily in the same location as today. The Southern Diner and Mrs. K's Toll House were famous for home-style food, as was the Hot Shoppe. Bonat's was as French as you could get in Washington. And, in the Thirties and Forties, if you were downtown at night, which was the fashionable place to be - social Washington took evening strolls around the Ellipse - you dined at Hammel's

This was a restaurant the national guide books touted as one of Washington's finest. It was noted for its German food, its deviled crabs and especially for its beef. But eventually its fame rested on Hammel's invention born of Depression thrift: Roast Beef Bones Diablo. It was the hangout of tax court judges and bureaucrats, a lively restaurant with waiters in white aprons.

Today, the Roast Beef Bones Diablo are gone and the waiters wear brocade dinner jackets.Downtown night life is, to put it gently, quiet. But with the new FBI building across the street, bureaucrats still crowd Hammel's tables at lunch, and the restaurant is probably the least changed of any os Washington's long established eating places.

One long-term resident of Washington told me she had never been to Hammel's because she doesn't trust restaurants you can't see into from the street. She would be pleasantly surprised if she ventured in. Hammel's has a clubby look, with strong contrast of dark wood and white tablecloths, chandeliers and elaborately framed paintings. A collection of gargantuan beer steins fills one corner, an electric organ with a Greek urn another corner. The cuckoo clock and the maitre d'hotel seem to have overseen that small room forever. The waiters, unfortuately, are newer, sometimes not completely comprehending English. The service is well meaning but slow.

Hammel's is these days clearly geared to lunch, when the closely spaced tables are packed and the cooler in the rear may be filled with pastries and strawberries. The menu at lunch lists about forty entrees and a dozen desserts, whereas the dinner menu is limited to half as many entrees and three desserts. It is at lunch one finds, in addition to a large choice of grills and seafoods, bratwurst with sauerkraut, sweetbreads with mushrooms, pigs' knuckles, and unexpected international specials such as "Le mousaka," lasagna and goulash.

At lunch the home-baked Italian bread is fresher - and very good. The main courses are accompanied by freshly cooked vegetables - paprika-laced by lyonnaise potatoes and zucchini, fragrant with oregano if you are lucky.At dinner you get more pedestrian potatoes and a salad with the heaviest house dressing I have ever tasted. At lunch, best of all, there is a full range of homemade pastries, which are noteworthy in this city where good pastry is a rarity. A real apple strudel, tart and flaky, studded with raisins and nuts. A Black Forest cherry cake heady with kirsch and frosted with real whipped cream. Rum cake with honest-to-goodness butter cream frosting. A napoleon crisp and nutty tasting rather than soggy and chewy - a little tough and the filling somewhat stolid, but nevertheless way ahead of its competition.

Maybe dessert isn't the place to start, but at Hammel's it is something to keep in mind, as is the coffee. Hammel's has been buying Swing's coffee for decades and brews it with a consideration that shows.

Now that it is clear that the fringe benefits are commendable and the menu interesting, some very specific advice is necessary. Hammel's uses good ingredients, but not always to advantage. Our oysters saute a l'ancienne started out fine, but the soupy sauce needed reducing. Sauerbraten came off heavy and dry. Black bean soup was appealing at lunch, but must have been hanging around the stove too long by dinner because it was far too salty. Potato dumplings: soggy and lumpy. Planked rock bass at dinner: overripe fish smothered in a thick sauce so mustardy it brought tears to my eyes. Before you order, look around and see what the regulars are ordering. We saw lamb chops and, after trying some, agreed they were excellent, cooked precisely. Marinated herring is an appetizer done properly at Hammel's, a generous sweet-sour filet smothered in sour cream and onion rings. Crab cakes are controversial; the lump crab-meat is fine, but a bit too heavy with bread, and boldy seasoned like deviled crabs; stuffed shrimp, too, was unconventional, more like shrimp blanketed with creamed crab. Good in its way.

In general, order simple dishes, particularly grills. The others are unpredictable. Even a beef kebab was overcooked dry meat with undercooked onions and peppers. Greek spinach-cheese pie, flaky crusted and tangy, was counteracted by dismal veal marsala, stewed slices of chewy veal in an acrid brown sauce with a lump of green-flecked noodles which the menu had billed as spinach noodles. Yet the extensive lunch menu continues to tempt, with crabmeat Louis and deep fried oysters, duckling bigarade and sweetbreads, not to mention the half dozen changing specials.

Since one expects to pay more at dinner than at lunch, dinners at Hammel's seem reasonable, while lunch borders on expensive. At dinner, soup, main course, salad and potato costs $6.75 to $10.50. Thus, with a glass of beer or wine and dessert - remarkably prices at $1 - you could eat for about $10 a person, which includes free parking. Lunch dishes cost $1.95 to $7.50 without the soup. Even sandwiches start at $2.50. So a three-course lunch with a drink would also cost about $10. On the other hand, $3.95 at lunch for those excellent lamb chops, with a $1 slice of apple strudel and a cup of Hammel's fine coffee would be one of this city's better eating buys. And even when the kitchen blunders, there is something endearing about this graceful aging eccentric.