Playwright Tom Eyen, who died in 1991, is about to have an unexpected sort of comeback. And in “Why Hanna’s Skirt Won’t Stay Down,” with its original star again in the title role, he reveals the real reason everybody flocked to downtown 40 years ago.

A key figure in the 1960s experimental scene, Eyen wrote musicals for the bathhouse-era Bette Midler and churned out dozens of dirty little plays. He cut his teeth as an off-color, off-Broadway ’60s fixture at Cafe LaMaMa, and then leapfrogged from the West End to Broadway and a Tony. His hit 1980s musical “Dreamgirls” will soon be a film starring Beyonce and Usher – a very glossy coda for such a quirky career. But if you catch one of his earliest works, now helpfully revived at the La MaMa Club, you’ll see that anything MPAA-approved will make him turn in his grave.

Before he hit the White Way (and even after), Eyen exploited exploitation – giggling, for example, over such camp cliches as “Women Behind Bars.” The crucial element of that generation’s work wasn’t formal experimentation – it was raunch. Sure, people were breaking fourth walls up and down the East Side, but mostly, they were taking off their clothes.

Going to a show at La MaMa already feels like a trip back in time. Forty years on and Ellen Stewart still brings her schoolmarm bell to bring us to attention, and she still bosses her audience into sitting close to the stage. But La MaMa, happily ensconced in a time warp of sorts, is now consciously looking backward. Last year, they revived Andre Serban’s “Fragments of a Greek Trilogy,” which was Christmas come early for all of us who hadn’t seen it the first time. With “Hanna” they again reveal a crucial bit of theater history. That it’s also a fine, disturbing playlet helps to sugar the medicine.

Helen Hanft plays Hanna, a ticket-taker at one of the XXX houses who likes to spend her payday out at Coney Island, standing over a breeze-hole. Watching her shiver over a subway grating, letting her skirt rise up to her middle, is less titillating than frightening. (If you cherish any tender images of Marilyn and her billowing dress, Hanna scotches them.) A young man, Arizona (Christopher Zorker) hangs out on the Boardwalk, too, though he spends his time preening in the funhouse mirrors. Though the two of them tell strange, intertwining stories of their affair, they never seem to speak directly to each other.

The play, which basically becomes two parallel monologues by narcissistic nymphomaniacs, has aged surprisingly well. Though the references to 42nd Street as peep-show row are out of date, Coney Island still wears the right dilapidated, sleazy air. Ms. Hanft touts a horrible red boa, and several pounds of bad makeup, but she wears the years with ease. In fact, the lascivious, vacant Hanna has extra dimension when played by a woman well past that “certain age.” When a 60 some-year-old’s skirt goes up, revealing pink tights and appliqued, ah, funny bits, it’s genuinely daring (by any generation’s standards).

Ms. Hanft (called, at times, the “Ethel Merman of off-off-Broadway”) deploys a wonderfully strident foghorn of a voice. Whether railing against her balding, Avon lady sister, or against the injustice of those who call her a slut (they have a point), Ms. Hanft makes her pitiful figure something fearsome. Unfortunately, Mr. Zorker hasn’t a tenth of her charisma. He readily strips down to his Stars and Stripes speedo, flexing and flipping his long hair, but he hasn’t the right tone or attitude for the material. Sure, Arizona likes to exhibit himself, but Mr. Zorker plays him as a showman doing funny voices and begging to be liked. He should take a look at his co-star. She clearly could let the lot of us go hang, and we love her for it.

Director George Ferencz can’t bring his younger actor up to speed, though surely there aren’t many who could keep up with Ms. Hanft. She ploughs through text, occasionally inaudibly, like she has an urgent appointment after the show. Her Hanna is a gorgeously Brechtian creature, frightening and slipshod all at once. So in a way, seeing the younger generation so dwarfed by her presence, Hanna may have taught us the lesson she intended all along.

Until October 16 (74A E. 4th Street, between Second Avenue and Bowery, 212-475-7710).