Hi again, Thank you all that have responded so far. I think I need to elaborate further . The 300F hardtop I am working on came with a rear speaker from the factory. According to Gil Cunningham's microfilm build code interpretation, this car is coded: # 427 - radio Golden-Tone ( 5-button) including rear speaker. Therefore the rear speaker was factory-installed, not dealer or owner installed. No, I cannot tell from looking at the rear deck where the speaker was originally positionned. And, yes, in case it does make a difference, this car did NOT come from factory with a rear defogger. Doesn't have one, never did. So far I have rec'd the following responses: Keith Langendorfer - rear speaker in CENTER location, no defogger, car thus equipped when new. Bob Merritt - rear speaker in CENTER location, no defogger . Wayne Wunderlich - rear speaker located in RIGHT ( passenger) side ( !) Greg Leggatt - center location ( but no explanation) For those who care to dig a little deeper, and have had their 300F's microfilm decoded by Gil, please let me know the radio code and whether the rear speaker is documented as factory installed ! Having the locatiomn information is not enough, I need to know whether the rear speaker in your 300F's was factory-installed, and that info can only be obtained from microfilm. I don't want to consider cars that have a rear defogger at all ; the factory speaker location for those might be different. Sorry to be a pest. Appreciate the help. John