| OK, the building is wired up with conduit or something and you don't want to kill power to the time clock? You should be able to take the screw out of the cover plate and slide it out over the cord. Take a flash light and look at the wires in the box and the conduit. If you see more than one conduit and a black or other color wire, white, and maybe a green, that is a sign it is sign something else is tied to it. Follow, or guess at how the conduit may run back to the breaker panel. Often it will go up to the ceiling, and then to the breaker box. Check any junction boxes. If it is the only thing on the circuit, its colored wire will not be spliced, or go off in a conduit towards something else. The white could be spliced to another white, or other unconnected wires may be in the conduit.
I don't know if the clock will draw enough power to get a good amp reading or not, or if you can get at the wires with a clamp on ammeter. If you get the same reading at the clock as at the breaker, with all the lights on and things drawing power from all the outlets, it should be a dedicated circuit.
The above means more poking around live circuits than I like to do. Might better be delegated to somebody with training, experience, and the right tools. | 
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