Scout is the first to find two pieces of gum, wrapped in tin foil, and sticking out of the knothole of the Radley's tree. The fact that there are two pieces means that one is for her and one is for Jem. This first gift appeals to children's appetites, it's fun, and is one of many ways used to start up conversations with new friends. The gum is a token of friendship specifically given to two children who entertain Boo as he watches them from his house. If the children accept the gum, it is as if they are accepting Boo and rejecting the stories that anything from the Radley's property will cause instant death. When Jem finds out where Scout got the gum, for example, he tells her to spit it out immediately and go wash her mouth out. He also says, "Don't you know you're not supposed to even touch the trees over there? You'll get killed if you do!" (33). Since Scout didn't die from the gum, though, Jem is not hesitant to accept the next gift is discovered later.
Jem is the one who takes the next gift out of the Radley's knothole. When they get home, they unwrap the foil to discover a purple velvet box with two very polished Indian-head pennies inside. One is from the year 1900 and the other from 1906. Jem says the following:
"Well, Indian-heads--well, they come from the Indians. They're real strong magic, they make you have good luck. . . like long life 'n' good health, 'n' passin' six-week tests. . . these are real valuable to somebody" (35).
The above passage tells what Jem thinks the pennies symbolize--health and luck; but they are also another symbol of friendship. Since there are two pennies, then one is Jem and one for Scout. This shows that the gift giver wants to be friends with both of them, not just one. The years on the pennies might mean something special to Boo, too, and he wants to share that with the children. For Boo, a person who is shy and never talks with anyone other than family, this is a big step. He's putting himself out there to make friends and the gifts symbolize his genuine efforts and kindness.