Viva 'show and tell'

''Quanto costa?'' Our Italian class was almost over for the day. ''Mille lire. Duemila lire. Duemila duecento lire.'' Our Italian teacher stopped. ''Have you ever seen any Italian money?'' she asked. She pulled several coins from her purse and began to pass them around the room. ''These are all 100-lire pieces,'' she said, ''worth about seven US cents.''

My hand went immediately to my wallet, which I'd bought in Florence two years earlier. In a little pocket of the wallet I'd hidden away three 100-lire pieces as mementos of my trip. I'd take them out now and then, just to remember what it had been like to use them, to live in Italy. Now, almost instinctively, I reached for them: I wanted to say, ''Here are three more coins! The real thing! Viva Italia!''

I'd gotten the coins out of my wallet before I suddenly felt a little foolish. For better or worse, feeling foolish at such moments is something that happens to twenty-six-year-olds. I was a graduate student in an accelerated class in beginning Italian; I was surrounded by basically dignified, serious people, who certainly had other things on their minds besides Italian money. I noticed they were mostly just glancing at the teacher's coins and passing them on. As I left the classroom I felt relieved at not having created a stir over a few coins.

Nevertheless, the incident reminded me of what a great ''show and tell'' fan I have always been. In giving it some thought, I recall that kindergarten firmed up my feelings about the matter, though it was hardly the catalyst. Long before I went to school I was taking toy cars, or pine cones, or whatever was around, to my patient mother (and to my less-than-patient brother and sister) and telling them stories about what I'd done with these objects - how I'd built a Golden Gate Bridge for the cars, or how I'd spoken to Martians via a pine cone radiophone. The toys simply made things happen in my life, and I typically wanted to share these events and creations with others.

I do recall one particularly delightful ''show and tell'' in kindergarten, during which my peers brought in and discussed everything from diapered dolls to palm-sized cars with wheels so smooth they could travel the length of the room with a single push. I brought in a set of four child-sized tools: a saw, a hammer, a crescent wrench, and a screwdriver.

All the tools were made of plastic. The saw was about six inches long, with a blade painted silver and a handle the color of wood; the hammer was about the same length and weighed about as much as a box of paper clips. I'd also brought in a small block of some very light wood - probably balsa wood - and I proceeded to explain to the class how one built buildings.

I sawed a little and hammered a little; the saw actually cut into the wood, and the hammer (fortunately for my self-respect) made little dents in the block. I have no clear recollection of what I did with the crescent wrench or the screwdriver. Something tells me that I managed to get the jaws of the crescent wrench on one of the bolts of my school desk but couldn't turn the bolt for fear of breaking the wrench. In any case, I believe I immensely enjoyed explaining the adult world to my peers - especially since my version of that world, like theirs, was to say the least a bit idiosyncratic.

I think it's useful to remember such events from childhood. For one thing, they sometimes explain our near-misses with embarrassment, such as I encountered in my Italian class. On the other hand, they are a kind of tradition. They remind us of certain charming things that we used to do - and that, perhaps, we're still capable of doing in revised form.

After all, the kindergarten ''show and tell'' was not some foolish pastime, better when outgrown. It was a kind of play in which we kids laid imaginative claim to the world. It was exuberant and optimistic: It enabled us to try out various grown-up activities with a child's confidence and inventiveness.

In the actual adult world - the one in which I'm now writing - that child's ''show and tell'' reappears in all sorts of compelling roles. It reappears in the novelist's love of his story, the poet's sudden rediscovery of an elusive beauty. It also appears in the mechanic's care for his well-tuned engine, the sailor's love for the wind and for his boat, the architect's love for the form and function of his building, the physicist's delight in the instruments that reveal to him that other, invisible world of natural forces. This list, of course, could go on and on.

All of this love and caring stems not only from a desire to make the world work, but from a fascination that it does work - that wonderful things happen or can be made to happen. This, I think, is an outgrowth of childhood, of playing such games as the ''show and tell'' I remember so well. Laying hold of the world imaginatively is wonderful, in the literal sense of the word: It captivates us with the range of possibilities. Although, in adulthood, this wonder can seem foolish at times - for it is, after all, hardly serious, or rather hardly solemn - it is in fact a rich legacy. It can re-instill in us the urge, the curiosity to explore a world that (as William Carlos Williams said about poetry) almost resists our understanding.