Certainly not the most common vintage saps out there, the Hunter Leather Sap worth looking at. Hunter offered 2 sizes, 12oz and 16oz and they are described as "POLICE SAPs - A great favorite for many years. Formed lead weight with spring steel handle. Covered with top grade cowhide. Long 1/2" loop for thumb grip".  The two pictured here are both 16oz versions, differing only slightly in the width at the head, but essentially the same. The more worn version is slightly lighter at 496 grams, while the newer version is 508 grams. The style is similar to the Bucheimer Denver with the trailing strap riveted at the butt end. Each sap is exceedingly flat and not overly comfortable to grip. The narrow edge would likely cause cutting if it impacted flesh over bone. The wide, flat, heavy face at the head would be devastating to whatever it impacted with a hard strike.   

See previous post for catalog pics of the sap.