Weights could also be added to the top of the pendulum bob to speed up the clock's rate.
An ordinary bicycle axle could no doubt provide the donor material and save the purchase of a special die to cut the thread on a bare rod.
The cast rating nut has the appearance of a water valve wheel. Here the underside is shown.
Invar is a nickel-steel alloy which has almost zero thermal expansion. Changes in temperature should not alter the rate of the clock.
The entire C6/C7 bob. Removing the small screws will allow the inner weights to be fitted and removed for examination.