nutool mortiser question

I've just acquired a mortiser which is labelled "made in Taiwan" and "to Nutools specification" from which I deduce that it is at best a copy of a then current (1988) Nutool machine. It is a solid cast iron machine about 5 ft high with "proper" controls for locating the workpiece.
Question - does anyone here own such a machine? I would like to get the correct specification for the balancing spring, which sits inside the pillar, missing from mine. Thanks, RS
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