Milwaulkee Chair Co. Office Chair

This office chair was purchased off of craigslist.com. It has a stencil/print of "BIRCH MAH." and "5/12-28" and "I G." Then I found a small sticker/stamp on the back of the chair that must be the company's emblem with Milwaulkee Chair Co. Milwaulkee, Wis. and a picture of a woodworker working on a chair. I did find someone online with an office chair from the same company...and they mentioned markings on the base of the chair. I looked and found as part of the metal base mold it reads Milwaulkee Chair Co. Pat. Oct. 20, 1914. There is a lever that reads "pull" which I am thinking it may allow for the chair to adjust higher or lower. There is also a knob that is attached to the springs. I'm not sure that this is for. However, I did also find a screw that adjusts up/down in order to allow the chair to rock back. It is heavy and sturdy with only a few abrasions which could easily be lightly sanded out.
Thank you for your expertise!