am assuming this clock has a pendulum to adjust a pendulum there is normally a small wheel towards the bottom mark the screw with a felt pen (now easy to count the turns )plus/minus
first get the clock so it has a even beat to it, adjust by putting thin card under one side of the clock or the other ,(till it ticks even) when happy give the screw on the pendulum a couple of turns clockwise now time it over 24hrs if it loses turn the screw 1 turn up again, time it again, sooner or later the clock (will gain ) we now start to turn the adjustment the other way by about a 1/4 turn each time.
wirecutterman, March 2010
