Sirollus Saccus' Hammer is an item in The Elder Scrolls III: Morrowind that, when used on either weapons or armor, increases the Armorer skill. It is one of the "Secret Master" items in Morrowind, along with "Secret Master" of the four Alchemy apparatus items, and the "Secret Master" probe and lockpick.
This item can only be obtained by purchasing it from the Hammer's namesake, Sirollus Saccus. It is a restocking item, so it can be purchased multiple times. However, the Hammer only restocks in quantities of one.