Looks like you have a vintage Gillette Slim adjustable. They were made of brass and then plated. If you are using a toothbrush, use one that is marked "soft" and go easy on the plating.
IIRC, you asked about making adjustments in your original post. Were you referring to the adjustments on the razor from 1 to 9? If so, 1 is the mildest setting with aggression getting more each step up the scale with 9 being the most aggressive setting. Just use whichever one you is most comfortable for you.
Bob