Optical Galvanometer Cleaning

[Cyberdragon]

I have a couple very old optical galvanometer boxes, the most complete one being a Rubicon one. The problem is they are full of cobwebs and crustyness, even on the tiny bits.

How would I clean the tiny galvanometer mirror without breaking the mechanism? I looks so fragile I'm afraid a cotton swab would break it (or leave fuzzies on it).