Description Greener’s Humane Horse Killer in .310 Greener Horse Killer caliber with a single round capacity and a 4.75″ barrel. Made in London & Birmingham. Brass Mallet cap and front base. Barrel marked with British Nitro Proofs and serial number. Up-arrow marked on the front base for Military acceptance. Used to euthanize horses during WWI. Models made between 1865 up to the 1960s. Must ship to a C&R or FFL holder. Condition: Very Good/Excellent with light scratches and handling wear. A few dings on the mallet end from light use. Clean rifled bore. Barrel Length: 4.75″ Serial: 11347 Manufacturer: Greener’s Caliber: .310 Greener Model: Greener’s Humane Horse Killer Book# 10-621