The object in the image is a slapjack, also known as a sap or flat sap, which is a type of impact weapon.
Description: It is a small, flexible bludgeon typically made of a heavy leather outer shell filled with a dense material such as lead shot or powdered metal. The one pictured has a flat, oval, or "beavertail" shape, characteristic of a slapjack.
Function: The weighted end is designed to deliver a powerful, thudding blow with minimal effort, primarily using wrist action.
History: These weapons were historically popular with both law enforcement and criminals due to their small size and concealability, though they are now often outlawed in many jurisdictions.
Disclaimer: This object is a weapon and can cause serious injury or death. The information provided is for informational and historical purposes only.