Denford VMC1300 - Rescued

[m_c]

Have you downloaded the wiring diagrams from the Denford forum?

My guess would be one pair is a tacho feedback, and the other a thermal cutout (probably the ones that have been looped). If there's a model number on the spindle motor, you should be able to find a datasheet.
Also, check to see what wire numbers end up at the spindle driver, as that would give you a good idea, as only the power (probably via a relay or two), and tacho feedback will go to the driver. The thermal cutout would form part of the e-stop loop.