This is for a adapting a Tecnomagnete QX303UMK6 EPM (Electro-Permanent Magnet) chuck to an ST120F controller.
Details on my blog here: https://serialhobbyism.com/how-to-use-a-tecnomagnete-qx303umk6-epm-chuck-with-an-st120f-st100-controller
The author marked this model as their own original creation.