The reporter doesn't often encourage salesmen to cross her threshold, but after talking with a bulletproof-clothing manufacturer the other day, she was so impressed she asked him to call. It wasn't merely the scope of his operation ("Forty-five independent representatives in the New York area") or his corporate claims ("The Cadillac of the industry--ask anybody, ask the police") that sold her, as much as his obvious care in his craft.

"I have a new item I'm working on, a bulletproof portfolio," said the purveyor, Bill Levine. "Prototype, just came off of the line, for your executive from your top 500 companies. I'm sending it back, though. They made it in Naugahyde. Somebody spending $300 for a portfolio, I told them, would want leather . . . . "

Quite right, the reporter agrees. Enough to have to brave a storm of bullets without having to face the nasty barbs of fashion as well. Also, terrorists being what they are these days, one might easily be executed for a lapse of taste. Not that she could quite figure out how one would protect oneself with a bulletproof portfolio.

"What can you do, put it up in front of your face? Who's got reflexes that fast?" she asked the purveyor, when he came to call with a stack of bulletproof merchandise.

"Naaah," he said, taking out what was indeed a tacky little leather-like envelope of unfortunate hue. "We design it for the diplomat, to be used in conjunction with driving, when a lot of problems occur . . . . They put it next to their side, see, between them and the door . . . . Worn with a vest, it protects all your vitals except your head, and we can protect that, too."

His company is Body Armour International, a new little outfit that has, in its first year of business, sold 4,000 items of bulletproof clothing in this country. A "fabulous" growth industry, bulletproof clothing, says Levine.

Industrialists, owners of little grocery stores, diplomats--all are fine customers. He recently sold an item to a priest. ("A priest--that's when I said, 'Oh, boy, I must be in the right business,' " he says.) True to the sanctity of his trade, though, he won't divulge names. It would break the cardinal rule of the bulletproof-vest wearer: Keep your mouth shut, don't let anyone know. Letter From New York He's annoyed that word went out that Nancy Reagan wears a bulletproof slip, if indeed she does. "What is that?" he says, upset. "They're gonna tell everybody so they can shoot at her head?"

Won't bulletproof clothing, of course, encourage folks to shoot at one's head?

Levine shakes same.

"That's your smallest target," he says, "Also, you can move it. Your torso, that's the spot."

He presents the line: a variety of under-the-shirt and over-the-shirt vests in blue, white, gray and brown. ("Comfort and concealability, that's the name of the game.") Raincoats are available, as are hats, though Levine sells few--they cover very little space. And you can send him a swatch from a suit and he'll make a vest to match.

All come in three "threat levels": Level I, at $325, which repels everything from a .22 to a 12 gauge; Level II A, at $415, which stops, oh, your .22 magnum to your .44 magnum; and Level II, which would do nicely for a 9 mm. submachine gun, but which, frankly, nobody in the private sector has bought--it's really for your SWAT teams, your professionals, says Levine, or for a war. He does say, proudly, that nobody has ever been killed while wearing one of his vests.

"The most anyone stayed in the hospital was 24 hours, and that was observation."

Business, as aforementioned, is splendid. Miami, New York, Texas--"all your big crime areas"--are excellent. Crime got Levine directly into this business, as a matter of fact. He had a butcher shop in a tough section of Brooklyn and when he tried to buy a bulletproof vest he found he could not. He persevered, got his vest, and soon had sold 40 to other merchants.

Yeah, it's true, he says, vests occasionally fall into the hands of the bad guys--"sometimes they're wearing better protection than the cops"--but all his vests have a serial number and are filed with the police, he says. No, he has never had to utilize the bulletproof vest he wears.

As for the argument that bulletproof clothing may encourage bigger and better handguns, or that this is a sorry commentary on the lives we live, he has a philosophical reply.

"A passive approach," he says. "No one's ever gonna kill somebody with a bulletproof vest."