Symbolism, Imagery, Allegory
You might remember the whole baby-in-a-basket motif from such places as the Book of Exodus and The Winter's Tale. You know the drill: the infant found in a weird bag somewhere other than a nursery is totally going to grow up to be somebody.
Jack is no exception.
The handbag that baby Jack was placed in is—as Miss Prism describes it—completely ordinary. Like any other well-used purse, it is worn from overuse:
Miss Prism: Yes, here is the injury it received through the upsetting of a Gower Street omnibus in younger and happier days. Here is the stain on the lining caused by the explosion of a temperance beverage, an incident that occurred in Leamington. And here, on the lock, are my initials. (III.145)
But hey! This commonplace container contains a baby of uncommon origin. Continuing this theme of disguise, it is no coincidence that this ordinary-handbag-containing-a-baby is discovered in a cloakroom—a place where outer garments like cloaks, coats, wraps, and scarves are hung. These pieces of clothing can all be worn to conceal a face or an identity (especially in a murderer-in-a-trench-coat kind of way).
Let’s move onto Victoria Station. There were two train stations at the same site in Wilde’s day, leading to two different places. The western trail, including the Brighton line, led to the wealthier parts of London, while the eastern road led to places like Chatham and Dover, which were less well-to-do. The fact that baby Jack is at the intersection of these two lines literally puts him in an identity crisis. Does he come from a poor, common family or a rich, aristocratic one? Lady Bracknell tends to look on the negative side and judge him as common until proven noble.
But there is another, more positive way to interpret his discovery at Victoria Station. Trains are all about moving people to the places where they need to be. If we take Jack’s presence at Victoria Station to be a comment on his social life, it might suggest that he will have great social mobility—he'll have success in climbing up the social ladder to a prestigious position.
This is foreshadowed by the fact that he’s found specifically on the Brighton line, the road that leads to the richer parts of town. And indeed, the story of Earnest is about Jack’s social advancement. In fact, he’s revealed at the end to be a true member of the aristocracy—he's part of the Moncrieff family, which makes him a worthy husband for Gwendolen.
So the scene of Jack’s orphaning contains aspects (like the ordinary handbag and the cloakroom) that make him seem common, but also hint at his true aristocratic background (like the Brighton line).