This passage from Chapter 4 of To Kill a Mockingbird, is said by Scout after having found two "scrubbed and polished" 1900 and 1916 Indian head pennies in the knothole of the Radley tree.
But Scout and Jem are nonplussed (completely surprised) by the discovery and bewildered about what to do with them because keeping money someone finds is not part of Scout and Jem's "ethical culture." That is, taking money one finds is equivalent to stealing, but eating the wild scuppernongs (a large white grape with a thick skin that thrives in Alabama, although originally from North Carolina, and that is named after a river) in Miss Maudie's arbor, or stealing a squirt of warm milk from the cow, or even picking "an occasional camellia" are considered acceptable behavior for children.
Because Southerners were almost all descended from those immigrants from the British Isles, and because few people migrated to the South before air conditioning was invented, a distinct culture was generated in this part of the country. And, part of this culture was the unwritten code for what was permissible for children to which Scout alludes.