Marlin Hammer Spur Complete – includes screw and wrench.
Provides A Sure Grip On Rifle Hammers
Knurled surface gives extra purchase to easily cock external-hammer rifles equipped with low mount scopes. Just slip over the hammer spur and clamp in place with Allen screws. May be right- or left-hand mounted. Hammer Exension Fitting Guide
Please note – Marlin changes the size of their hammers in 1983. Pre-1983 guns need the smaller, old style spur. Rifles can be dated from serial numbers, using the following page – Link
For 39A, the old style spur is required.