A hammer for a percussion lock by Thompson Center, for their Hawken or Renegade rifle. The photo is representative! This used hammer is in very good condition.
Right hand, the hammer is factory engraved, and color case hardened. This is the early style hammer, with straight-up finger spur. The nose cup of this early style hammer requires the longer nipple. Later T/C locks have a hammer with a curled finger spur, and they require the new short nipple.