I just recently bought a handful of old tools from an auction and found this Brown & Sharpe inside mic in the mix. Unless I'm just missing it entirely somehow I can't seem to find a model number on it. The only text on it says "Brown & Sharpe Mfg Co --- Providence RI, USA --- Pat. Jan 29 - 1907". I'd like to be able to get some info on it such as how old it is and how to adjust it.