Guido,
Can you take a picture? Unless the P.O. changed out your entire system, I'm quite certain no Bose products were ever put in 500Es. If they were Bose, they'd each have an amplifier attached to the speaker (that's how Bose always did things, and in many cases still does). Rather, they had what the factory referred to as a "typhoon" system, which was a premium, optional 300E item. Should be a nice upgrade for W124 folks