Paul Marvel, whose business card claims that "Others' Losses Can Be Your Gain," is sitting on the Ocean City boardwalk. He is emptying out a pocket of his canvas apron and counting up the losses that have, within the last hour, become his gain: One plastic elephant, one plastic tiger, one Tonka toy crane, one toy aircraft, two pennies and a dime.

The tide is working its way out. The sun is pulling back. The beach that was plastered with an array of towels, umbrellas and ice chests, is slowly yielding to the quiet of the night shift: Out come the metal detectors, a devoted corps of scavengers who scour the beach, sift through the sand and stake a claim to others' losses.

Every summer, Ocean City swells with vacationers -- more than 200,000 a day, according to Robert Rothermel, executive director of Ocean City's Department of Tourism. Although most metal prospectors value the solitude of the uncongested beach during the off-season and prefer to avoid the public glare, the peak season offers an obvious advantage: "The more people, the more chances they'll lose something," said Isaac Clark, 56, of Cambridge, Md.

Three or four times a week, Clark drives 65 miles from his home to Ocean City to walk up and down the beach with his White's Coinmaster 6000/D Series 2 detector. Clark, like other prospectors, comes to the beach not just to find buried treasure, but to find solace in the salt air, the seclusion and the sea.

For Clark, the exercise is therapy for his poor circulation and weak heart. The companionship of fellow prospectors and the unpredictability of the hunt help his spirits, which have been low since he quit working several years ago, he said.

Some of the losses and gains in the metal detecting food chain are negligible: flip tops, bottle caps, scraps of foil, empty ketchup packets, beer cans, a broken fog horn from a boat and so on. The veteran prospectors abide by a code: They pick up the metallic garbage, stash it in the "junk" pockets of their aprons, and throw it in trash cans later.

"I've never seen a farmer plant weeds in the garden," Marvel said, "so I don't see any reason to put the trash back in the sand."

"We pick up the things we get beeps on," Clark said. "This way, they won't be here when we come back again, and the next metal detector won't have to pick it up."

Metal detectors: These are the people who appreciate a good Northeaster -- a wind that cuts into the sand, pulls it back into the ocean, recirculates the metallic treasures, and exposes a new layer of beach rich with metal-detecting possibilities. These are the people who share the early morning beach with the hungry gulls, the Ocean City beach maintenance crew, the fishermen and the deserted boardwalk.

They know that the high beach is filled with pull tabs. But they know that if they switch their detectors to "discrimination" and shut out all the beeps from the pull tabs, they'll also miss out on the nickels and other goodies. They know about the cheap zinc pennies the government now issues -- so easily corroded that they're not worth the battery power it takes to detect them. They know that when a woman enlists their help to track down a ring she lost in the surf, it's a hopeless cause for her, and a future good fortune for a metal detector. And they know the rewards are limited.

"It's a good hobby," Marvel, 49, said. "But you don't get rich."

Marvel, who lives 20 miles from Ocean City, in Frankford, Del., has been metal detecting since 1969. Two years ago, he took an early retirement from DuPont, where he worked as a mechanic, and now puts in long hours treasure hunting. The little two-door Datsun that he drives could be the only car around that has a hood ornament in the shape of a man holding a metal detector.

In the back of his house, Marvel keeps a small shop where he sells metal detectors, scoopers, headphones, aprons and other items. The shop hours are irregular, if for no other reason than that the hours he spends on the beach detecting are many and erratic: early morning, late afternoon, middle of the night, six hours one day or two hours the next.

He sweeps the beach with the staccato rhythm of a windshield wiper -- small, quick steps across the sand, each step punctuated by a swift wave of the detector. There is a purposefulness to this coordinated movement that sets Marvel apart from the dozens of other metal prospectors.

On Marvel's left wrist is a watch composed of three different "finds." The band, the clasp and the face, he said, "are all from this beach in times past." He pulls a keychain out of his pocket and said: "Every once in a while, you find something nice. Just about once a year I find a Spanish coin." And one of them, a 1777 silver coin that Marvel said he dug up a few years ago, now dangles from a keychain.

But the beach is a humble lottery that does not make millionaires. When Marvel sells metal detectors, which cost anywhere from $99 to $700, he tells his customers "to think of the metal detector as a fishing pole or a shotgun. When you go out deer hunting or fishing, enjoy yourself. When you go out metal detecting, if you do pull in a few coins, a couple of dollars, okay. But don't expect to go out and pay for it."

"You get a nibble, you get a nibble, you get a nibble and then you get a bite," Clark said of the pasttime.

And if there are too many nibbles -- too many zinc pennies and too many pull tabs -- there are also rewards.

This summer Clark has found "a few nice things" -- two diamond rings. Clark says he rarely seeks out owners because the few times he did, he got no response.

"It's always something that you are finding," Clark said. Finding and, in his case, saving: The only thing he has sold during his five years of metal detecting is a 1912 Cambridge dog tag, which he sold for $15 to a man who collects dog tags.

"All I talk about all the time," Clark said, "is what I find": false teeth, fishing sinkers, toy cars, class rings, keys, Little League baseball pins, Cub Scout badges, hypodermic needles, pocketknives and coins.

"At night, when I'm tired and lonesome," Clark said, "I look in my coin book -- I have every coin I've ever found, marked with the date and place. It's very joyful. You can remember everything you've found and where you found it.

"I'm not the kind of person that saves bottles and cans," Clark said. But those are just about the only things he doesn't keep. Clark collects and records in a log book everything else. Even the more than 100 hair barrettes that he has picked up. For amusement, Clark likes to look at the barrettes periodically and think about the owners.

"You get so that you can tell a lot about the person that had the barrette. The affection that the parent had for the kid -- you can just about figure out what kind of dress she was wearing."