It is new, just installed. I believe the serial number is printed on the side of the unit with other information, but not the SEER. I just want to make sure that I got the 12 SEER unit I paid for. After the install the only literature I received was the install manual.
You need the outdoor unit model number and the indoor unit and or coil model number. Outside of that if you just want to know the outdors inteded seer, look at the yellow energy guide, it shouldnt have been removed by the dealer. If you didnt have the indoor unit changed, then your guess is as good as ours as to what its rated or not rated as.