I was cleaning an Aaon condensor coil today which I have cleaned several of these at a bunch of Wendy's. This one was different, at first it appeared to be a completely copper coil. fins and tubing. then I noticed the copper chipping off at the bottom and at the very top of the coil, also I could tell it was aluminum on the backside of the coil. even the frame around the condenser coil appeared to be copper. this unit is about 10 years old. is this some coating they tried to see how it would work?