Contents, as of last inventory: one key of unknown provenance, two dead watch batteries, a single earring, a rubber band gone brittle, and sixty-three cents in mixed change, none of it useful in a vending machine built after 2003. The spare key bowl sits just inside the front door, on a table or shelf sized for exactly this purpose, and functions as the household's most honest archive, not of what matters, but of what was, at some point, worth setting down rather than putting away properly. The bowl itself is ceramic, or occasionally wood, occasionally the lid of something else entirely, repurposed after its original contents were forgotten.
No key in the bowl has been tested against a lock in recent memory. The working theory, held by every household with one of these bowls, is that a key kept is a key that might someday matter, a shed, a storage unit, a house two addresses ago, and the risk of throwing away the one key that matters is judged to outweigh the near-certainty that none of them do. Coins collect at the bottom in a fine sediment of pocket change too small to bother banking. The bowl is emptied only during a move, its contents examined once, briefly, with the specific puzzlement of an archaeologist who has found the right layer but the wrong civilization, then transferred, unsorted, into an identical bowl at the new address, where the question of which key opens what will presumably be answered by someone, someday, though no one currently living there is prepared to say who.