Summary

This model is a clip probe for electrical measurements.
It uses a piece of copper wire (0.8 to 1.4mm diameter) and a spring (up to 8mm diameter). A pen spring works well.
Follow the illustration in the pictures to bend and install the wire. The twisting with a drill is important as it not only straighten, but also strengthen the wire by work hardening.
You can then solder a cable at the tail to use the probe.