He had found a lovely button in his poverty and had sewn it into the inside of his coat just over his heart. It was his only treasure. The one thing that made him feel as if he had "something." He had nothing of real value to give as the world assigns value, nothing the world considered precious, but he did not let that stop him from giving. He trusted John to comprehend the weight of the gesture.
You know the grace of our Lord Jesus Christ. You know that Christ was rich, but for you he became poor so that by his becoming poor you might become rich. 2 Corinthians 8:9
(The button above is from an ad on Etsy as I did not have a picture of John's which is similar but has a lily on it.)