Open Monday through Saturday, 6 a.m. to 6 p.m. No credit cards. No reservations.

DOWNTOWN luncheonettes, Barney's among them, are archives of the signs of the decades. Barney's, a long railroad-car-shaped eating place with a blue formica counter and tiny two-person booths, tells you in three different places (at least) to please pay the cashier. Several walls remind you that the restuarant serves mixed drinks and cocktails, and behind the counter signs that are nearly antiques depict specialties like milkshakes that apparently have not been served for years. Otherwise, Barney's is beige, about the color of vanilla wafers, a theme repeated in the color of the plastic dishes. And the primary decorative feature is the artfully stacked boxes of Rice Krispies and Frosted Flakes.

A delicatessen so undesigned must be good. And in some ways it is. The sandwiches are big, though they look even more so on the tiny plates used to serve them. The bread is no better than the beige and brown flab served around Washington. But the turkey is freshly roasted, cause enough for celebration. The chopped liver has chunks of chicken liver in it, which not only lets you know it is made on the premises and that it is chicken rather than beef liver, but it tastes wonderful that way. No grandmother would turn in her stockpot for the chicken soup, but it is good enough, and with a big fluffy matzo ball it is raised to a very respectable state. If you like sour cream, try the borscht, which is about half sour cream. And if you like celery seed, try the potato salad. Most sandwiches at Barney's cost $2 to $3. Most are made with the usual precooked corned beef and roast beef; with them you get a decent pickle and, if the place is not too busy, which hardly ever happens, a smile from the waitress as she deposits it on the run. The waitresses try hard, but they need help. And if you order a three-decker sandwich at Barney's (how about turkey, corned beef, salami coleslaw, lettuce and Russian dressing?) you, too, may need help.