If the buyer can prove to their own satisfaction that the enlarger meets their requirements, then often the buyer can get a bargain.
Most private sales of this type are "as is".
Perhaps you've heard of the motto caveat emptor. Even if the seller says the enlarger works, it is in the buyer's interest to know it enough to figure out whether or not it actually does work to their satisfaction.
You are free to buy a used car from a used car salesperson without a test drive just on their say-so that it works. I choose not to.
Page 7 of Dual Dichro S manual
The Dual Dichro S operates on standard household current [120 volt, 60Hz US and Canada] and may be plugged directly into an AC wall outlet without the need of an additional power supply. There are two power cords which must be connected (Fig 24) for the unit to operate. The balck cord (marked “To Timer”) should be plugged into your “enlarger” outlet of your enlarging timer and the gray cord (marked “To Wall Outlet”) should be plugged directly into an AC wall outlet (Fig 25).
To protect against line voltage fluctuations which may cause undesirable color and density shifts in your prints, a voltage stabilizer is built into the colorhead. Do not plug the colorhead into an accessory stabilizer.
To operate the colorhead, make sure the main power switch (Fig 24) is on and follow the instructions included with your enlarging timer.”
To safely test the bulb and its circuit without a timer, you can first plug in the gray AC chord into a wall outlet and switch on the power switch to engage the cooling fan.
Now you can plug in the black power cord into an AC outlet to engage the bulb. If everything is working, the lamp should come on.
Ian - That settles it! Brilliant. Thanks so much for your time!