Shelly's wallet was the wallet of Shelly Finkelstein.
The wallet contained not only his money but a valued picture of him and his mother.
The wallet first came into the plot in a grocery store in town when both Shelly and Vera went to town in Rick's car for groceries for the Wild Bunch. Vera forgot her wallet and thus had no money to pay for what they had bought. Shelly gave his wallet to Vera to pay for the groceries. She forgot to give it back to him due to the trouble in and out of the store from a group of bikers.
After Shelly walked off after Vera had chastised him from playing another prank, she took the wallet out of her pocket realizing she forgot to give it back to him and looked at the picture of him and his mother. Touched by this, she sympathized with him and decided to find him, talk to him, and return to him his wallet but she dropped it in the lake by accident. Just as she got the wallet out of the lake, she saw a person that she thought was Shelly and tried explain but was killed by a harpoon to the eye after she realized it wasn't Shelly. The wallet dropped to the ground as Vera fell into the lake. After the massacre, it was found by the police during their and the paramedics recovery of the bodies and investigation of the area but that was never shown. Shelly's wallet and his "whole world" still in his box (including the hockey mask) was buried with Shelly's corpse, after the picture was taken out.
It was the last bit of her would-be boyfriend she ever saw again before she died.
- Friday the 13th Part III (1982)