I have obtained an an antique Philip Harris balance scale in good, but condition aside from a lot of corrosion on the brass. I can't find a model number on it and am not sure of it's actual age, but I am guessing 1950's. It has a chain-dial on it, which is something that I'm not familiar with. I've not been able to figure out how to actually use the chain-dial or indeed any information on them. In cleaning up the scale I found that the guide for the plumb line was not correctly attached so it's possible that the chain-dial isn't attached right either.
Can anyone explain in detail how the chain-dial is used or direct me to some documentation or textbook resource on using a scale of this nature.
