this clock may have a pendulum fitted if yes you turn the small wheel on the pendulum upwards to make the clock gain and downward to slow it.
mark the knurled nut with a felt pen, now adjust it up a couple of turns,time the clock over 24 hr period, keep adjusting it again till you get within a minute a day,
I,ve seen different versions of 8 day smiths that can have a floating balance wheel this can be adjusted on the back of the clock externally, others versions are internally above the floating wheel
wirecutterman, August 2010