Lear Aviation makes jet planes, but Lear electronics makes amplifiers and stuff. As far as I know you can still get Lear car stereo gear. It still could be part of an aviation system though. Small PA system in the plane, headphone amp for the pilot, etc.
Those selenium rectifiers - lower left pic1 - are itching to be replaced. All those wax covered caps underneath will be leaky. And the electrtolytics as well.
This is clearly an audio amp. More than that I can't tell you.