It looks like it came off a V8 engine from the early fifties. General rules for oil bath air cleaners. Unscrew the wing nut and take the top off, the inside is filled with filter material, horse hair or some synthetic stuff. Soak this in kerosene or Varsol and swish it around, then let it drip dry. Do not blow air through it. You will make channels that will let unfiltered air through. Pour the oil out of the base. Wipe the dirt out with rags or cotton waste. Refill to the oil level mark with straight 50 weight oil. In below freezing weather you can use 30. Wet the filter with oil, or pour a little oil over the filter material and put the filter back on. In normal driving check the filter whenever you do an oil change. Top up the oil as necessary. If the oil reservoir is more than half full of dirt and sand, clean the filter and start over. You never need to change anything but the oil. On good paved roads, you can go at least a year or 10000 miles before servicing. In a dry desert climate maybe half that. In really extreme conditions, like a dump truck working on a dusty site or driving through a sand storm it may be necessary to service the filter every day.
Nice acquisition it has potential. Not sure what make and model it is from, but 50's most likely. Check out my thread where I modified my 50's Chrysler oil bath air cleaner... http://www.jalopyjournal.com/forum/showthread.php?t=795932