The center pin hole through the cylinder is 0.128". The pin would need to be a minimun of 1.75"
The hammer is double action with a hammer nose and an internal hex head screw as its pivot, the trigger is also pivoted by a hex head screw.The hammer for the small frame HS 21 would not work.
The hand pivots off the trigger and is sprung with a coil spring
This pistol has a left side plate held on by a single screw at the rear covered by the grips.