AMATEK Model T Dead Weight Tester

My school has asked me to recondition some donated calibration equipment. The DWTs are supposed to be EXTREMELY precise pieces of equipment and the condition they're in is nothing short of a crime. I've brought one unit back to life and I'm waiting on parts for the second one.
The next step is attempting to restore the weights. I'm not even sure what they're made of. "Green and crusty" would be a fair visual description. Since they're​ very precise weights, I'm reluctant to take a wire wheel to them for fear of removing material and throwing the weight off.
Does anyone have any suggestions for removing what I *think* is corrosion or oxidation? I'll post some pictures tomorrow afternoon when I swing by the lab.

Sent from my Pixel XL using Tapatalk

Depending on how precisely these things have to be calibrated I doubt that you'll find any method of cleaning
that doesn't remove at least some of the parent material. This means that re-calibration will be necessary so I
would start by finding a place to have them calibrated and see what they have to say...