WE'RE HISTORY already, we children of mid-century. The Smithsonian says so, so it's gotta be right, right?

I mean, if you've been feeling a little creaky in the joints, Baby Boomer, if your wind is weakening and your mind is wandering, hobble on down to the National Museum of American History and you'll really feel old.

They've got the toys and dolls we played with, the television shows we watched, the school desks we ducked-and-covered under, enshrined as historical objects, artifacts from olden times. Grown-up people are wandering through the gallery saying wow, lookit that quaint old stuff.

How old are we children of the '50s? Well, Charlie Brown turned 40 this year, guys and gals, so you can take it from there. In fact, you have to take it from there, because the exhibit is an elaborate do-it-yourself kit. It asks more questions than it answers about how it was to grow up between World War II and Vietnam, in a world glistening with the promise of prosperity for all and shadowed by the threat of the mushroom cloud.

Which is commendable restraint on the part of curator Charles McGovern; he's a mere 32 years old, what does he know?

The show uses a question-and-question format meant to stimulate thought rather than lay down an official version of contemporary history. The exhibit brochure goes so far as to admit that the Smithsonian doesn't have all the answers, and invites the patron to submit variant versions of history or herstory.

As far as I'm concerned, the museum's got it about right, except that they've slighted Buck Rogers and Senator McCarthy, the two most vivid offworld characters of my adolescence. But there's never enough space and you always have to leave a lot out. McGovern knows, for instance, that we didn't all grow up in middle-class suburbs, but that was the focus of the American dream back then, and that's what he has tried to evoke.

For me the shock of recognition that rent the veil of time was the floor plan for a suburban tract home that shows the family room opening onto a barbecue room. Proust had his madeleines, but my remembrances of family life are all sicklied o'er with greasy smoke and the tang of charcoal lighter fluid on half-burnt hamburgers. I dunno how it got started, but a backyard barbecue pit conferred status in those days; my father built one that required about three thousand of brick and could have roasted a medium ox.

The exhibit doesn't neglect the darker aspects of cold-war conformity and the grotesque consumerism symbolized by those bizarre auto tailfins. It leaves us with disquieting questions about whether we came through the experience with sufficient knowledge, courage and character to fit us for raising our own children.

Whaddya think, kids? THIS IS YOUR CHILDHOOD, CHARLIE BROWN --

Through April at the National Museum of American History, 12th and Constitution NW. Open 10 to 5:30 daily. Metro: Federal Triangle.