Here is some stuff that may be of use. ITR were a subsidiary of IBM until the 1960s when they were spun off. They were located in Hammersmith, England but have no idea what has happended to them recently. A lot of these clocks were branded IBM so try searching on that. British made equipment should have a 'voltage plate' somewhere near the power cable input saying what Voltage it needs and what Current it consumes.
British equipment runs at 240v 50hz. I can think of no reason why it would follow the US standard (110v 60 Hz.), unless made for export to the US. (Most of the world does not use 110v 60Hz. - believe it or not!) So if UK built for UK use, your machine's input voltage is almost certainly 240v at 50Hz.
To run a 240v device at 110v you need a step up transformer BUT that will not deal with any frequncy variation, so any frequency dependent devices (e.g. motors) will run slow. HOWEVER your statement: "I have found reference to a dropping resistor used to run USA clocks on 240v." leads me to believe that you don't know a lot abut electricity AND your box may have been converted to US voltage. So why not take some professional advice before you shove 240v into it?
Terry
February 2006
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