Tork 8600 is variable cycle timer. Each revolution of dial is 60 minutes, 30 minutes or 6 minutes depending on model. 60 minute timer has 2 models, 120V and 240V. Other models are 120V. If clock is not keeping time, then clock motor is bad.
I don't have a source for clock motor, and suspect that a new timer is purchased and then installed into existing box. Link below sells 8601 60 minute 120Volt To set times, the dial has tabs located around dial. Tabs are tilted in or out Tab out = NC terminal has power Tab in = NO terminal has power Nov 14, 2010 .