The board I'm looking at is a modem board from a fax machine.
There are 2 identical components labeled VZ1 and VZ2 on the board, both components have F175 on the face and have 2 SMC leads.
One of them has a resistor across the back pins, and they look like they might be part of the power circuitry.
Best Answer
VZ is sometimes used as the designator name for zener diodes. VZ1 and VZ3 look like 2-lead packages, so that fits.
Take one off the board carefully. Put a 10 kΩ resistor in series with it, then connect that combination to a power supply, like maybe 24 V. Measure the voltage across the device, flip it around, then measure the voltage again. If it is a zener diode, then it will be 700 mV or so in one direction, and some volts in the other. That latter is the zener voltage.