slim black object on 1st generation macbook air case This is just a curiosity: what is that slim black part (see picture) in the Apple Macbook Air 1,1 (Early 2008) case?
According the Apple's user manual it is the Infrared Receiver.

http://manuals.info.apple.com/MANUALS/0/MA394/en_US/MacBook_Air_Users_Guide.pdf

The "Sleep Indicator Light" is next to it on the left.

The MacBook beneath it has the same configuration.