Inside a "Werkometer Regel-Trenn-Transformator TG1" isolating transformer

This is an old "Werkometer TG-1" - a variable AC voltage isolating transformer. It is used to gain some safety against electric shock while repairing old radios and other mains-connected hardware (by providing galvanic isolation).

The unit´s circuit plan for those interested:

Inside, we find a huge copper ring coil:

Here another shot:

greetings noq2