52 vac electrical question

When I purchase this tractor, it had the standard 6v generator but was running a twelve volt system. The coil is 12v and the battery is 12v. When you spin up the generator it puts out 12.6 volts. Everything seemed to work fine. The original light switch was gone. I recently restored the tractor and plan on hooking it up the same way (unless anyone has some words of wisdom) My question is the part that attaches to the generator a regulator, or a cutout and does anyone have a part number wher I can get a new one. Here is a picture. I appreciate any help as to what this is and what was done with the electrical system.

Type A. You disconnect the field wire from the VR (voltage regulator) and touch it to Ground. If the Gen is full fielded (has output) you need a Type A VR.

Type B: You disconnect the field wire from the VR (voltage regulator) and touch it to Battery. If the Gen is full fielded (has output) you need a Type B VR.

Hope this Helps,