It's five minutes before noon-time on a sultry day and 60 people are already waiting in line at Mother's for their lunch. The regulars pass the time drinking beer. The help seems resigned to the fact that the customers will be on their way as they carry the fried fish fillets, French fries, sliced beef and soup from the kitchen to the front counter. "Watch ya all legs," is the cry as a steaming cauldron of gumbo goes by.

Mother's is the home of what many New Orleanians consider their most famous indigenous dish. Not gumbo or pralines, but what natives call a "Po Boy" and everyone else knows as a Poor Boy sandwich. One local critics says, "the core of our eating tradition is the Poor Boy. It is the work of a genius." Leave it to a New Orleans native to extol the virtues of a sandwich as if it were a souffle.

As with so many other New Orleans dishes, the Poor Boy is the anglicization of a French expression, pourboire. The slang expression for a tip, literally meaning "in order to drink," it was used by porr children here years ago as they begged for money. Instead of giving them cash, convent nuns would feed their sandwiches made on long loaves of bread that had been sliced horizontally and filled with slices of meat, cheese and whatever else was around.

Other restaurants sell Poor Boys but Mother's, located in a seedy building surrounded by warehouses and empty buildings, has won the distinction of serving the best of its kind in city that prides itself on its food. Where else in the United States are the city's restaurants among not-to-be-missed historic landmarks?

This may help to explain why fast-food chains do not appear to have made the same inroads here as they have elsewhere. It probably also accounts for the fact that people with only an hour for lunch are willing to spend 35 minutes of it waiting in line for a sandwich.

To be sure it is a rather impressive sandwich; eating it is far more enjoyable than describing it.For $2, crusty French bread is served with a filling of oysters, fried fish fillets, roast beef or roast beef and ham.Opinion is divided over which is the best at Mother's - the beef and ham or the beef alone. The beef and ham, called a Ferdi, after a man who kept ordering it, is the most popular. Those who prefer the beef alone say the ham overpowers the beef.

The meat is sliced and served on bread which has been slathered with pan juices from the roasted beef. (The juice is enriched with lots of little scraps of meat left over from the slicing.) It is topped with shredded lettuce, pickles, mayonnaise and Creole mustard, a dark mustard enlivened by horseradish. One bite and the sandwich leaks - all over. It isn't any good if it doesn't, aficionados say.

The local customers who frequent Mother's come in all sizes and wear costumes that range from grease-covered T-shirts to Marine uniforms for the men, from short-shorts to fashionably long dresses with stockings and high heels for the women. Now that hotels have been built in the area, tourists are coming too, making the restaurant more crowded than ever. But the owners, Jacques (pronounce it Jack) and Edward Landry, aren't about to enlarge the place. "That would ruin it," says another brother, Ben, who works there.

One of the patient waiters-in-line said he'd been going to Mother's for 30 of its 41 years. "You know your stomach's in good hands here. Simple good food, no hanky panky. They don't grind up frozen meat from South America or put in any extenders like the fast-food restaurants. That's why people come," he said.

"I come because they've got the best Po Boy in town because they put more meat in it," another explained.

The Marines come because the Landry family's association with the Corps is long and abiding. The father, Simon, who founded the restaurant, was a Marine during World War I. His four sons and one daughter were Marines in World War II.

The walls are covered with citations from presidents, letters from Corps commandants, pictures and other service memorabilia. The Marines call Mother's Tun Tavern, after the Philadelphia landmark where the Corps was founded.

But the brick walled, cement floored establishment has none of the spit and polish of that formidable organization. Which is part of its charm. There's no tipping, mostly because there's no service. You pick up your own order, then try to find a place to sit. You're lucky if the table has been cleared before you get to it.

Everything is made at the restaurant. The fish are fried a few at a time, so are the oysters and the potatoes. Only the beef and ham are cooked in bulk. The ham is started at 5 a.m. Rounds of beef, weighing from 70 to 110 pounds, cook all night covered in foil, with carrots, onions, salt and pepper. Mother's serves over 1,000 pounds of beef a day.

"A lot of people may get a little peeved because we run out of things, but the ovens are going 24 hours a day," Ben explained.

He and Eddie get in at 4:45 a.m. to join Jacques, who has been there since 2 a.m. baking biscuits for the breakfast trade. The restaurant is almost as well known for its homemade biscuits, grits and "burnt ends" as it is for its Poor Boys. "Burnt ends," in case you're not a native, are the ends of the baked hams.

In praising Mother's and its Poor Boys, one restaurant authority equated a visit there with a meal at any of this city's top restaurants.

Quite a compliment for a sandwich that got its name from a bunch of urchins.