Strange Oiler

Below are some pictures of an unusual (to me) oiler that I am trying to figure out what it was originally used for. There is a central plunger that appears to actuate a pump within the glass chamber and also a small cam action lever that seems to work like the on/off valve on a typical engine or machine drip oiler. The metal cylinder has a gauge with markings I have never seen before.  The metal parts all appear to be nickel plated brass.  If you can help with information please contact me at the email address below.

Thanks,

Larry