The quiffs are combed, the faces shiny. A previously unseen photograph of John Lennon, Paul McCartney and George Harrison playing guitar together in a Liverpool front room, before they became the Beatles, has given fans a fresh glimpse of an early moment of musical alchemy. Although it was published for the first time this Easter to commemorate the day the band hung up their instruments and turned their backs on each other 50 years ago, this grainy shot looks familiar.

Somehow, everyone already knew that these three boys once stood together like that, laughing, in rockabilly garb amid the trappings of postwar, lower-middle class gentility. The image is a confirmation, rather than a revelation, despite the fact it has not been seen before and that both the exact location and the occasion of its taking are lost in the past. The Beatles’ early story is such a part of a shared, imagined history.

In 1959, snaps of youths hanging out together were a real novelty, no matter who the subjects grew up to be. Before long, though, stacks of forgotten paper wallets full of badly composed photos of leisure-time frolics became commonplace. And today infinite streams of images of young people having fun adorn the internet and smartphone memory banks.

If it is rarity that marks the value of an item of currency, as much as its sentimental significance does, then pictures of teenagers have slid right down the monetary scale. They are now worth much less than two a penny. Except for this spring. Photographs of teenage musicians giggling as they learn to play their instruments together are not being taken right now. When we can see them at it again somewhere, the images will have true value.