Cigarette Case
Jack's cigarette case is a symbol that he has another life elsewhere that he has not shared with anyone in London. This is what Alge uncovers at the beginning of the film.
Jack
Ernest's real name is Jack, when he asks if she could marry someone with the name of Jack she says no, it has no music in it. This is a symbol of the class structure that is ingrained in the British culture to be accepting only of what is said to be of high class, and the fact that Gwendolen says the name Ernest has music in it means that what one hears determines the status of the person. Not the actual person.
Handkerchief
Ernest has a handkerchief up his left sleeve that he pulls out and dabs his head of sweat. This is a symbol that he is being roasted by Lady Bracknell while she asks him questions to determine if she will allow him to marry her daughter.
Black Bag
Jack keeps the black bag he was found in behind a glass case. It is a symbol for his longing to know who his parents were, and his clinging to wanting to know his identity.
Diary
Cecily keeps a diary with her at all times. It is a symbol of her holding on to every word that Ernest has sent to her, a catalogue of every conversation they've had during their romance.
