So I recently moved into a house (I'm renting) and it's getting chilly so time to turn on the furnace but I wanted to replace the furnace filter first. Went to the basement to look at the beast and jeez I feel dumb 'cause I can't find the filter anywhere!! It's an OLD Milwaukee Thermoflo Furnace. Model 1203-C11. Serial# 68931. I just need to know the size of the filter and where it goes! I've looked online for a manual too and come up with nothing. Any help you could give would be appreciated. Thanks!