oil leak?

So I am slowly preparing to do the spring thaw on my oval. Went out today just to look things over and I notice that there is a small amount of oil sitting in the well of my bottom pulley. There is some dampness in the well under the pulley, so I check behind the pulley to see if there is any oil behind the pulley. NO. Since I am a bonehead when it comes to being a mechanical detective, where is the likely source for this oil. Again, it's not a gusher as the amount (about a thumbtip full) accumulated over the winter. But still a bit unsettling as I see no obvious source. This on top of still not being able to figure the source of losing brake pressure (master cylinder seems dry, pedal assy is fine, rear brake area seems ry). - DB