Advent loudspeakers

Didn't the first Mustang come out as a 1964 1/2 ?

Mustang production began in April 1964. For various reasons, including a lack of parts due to overwhelming demand, it stopped in June 1964. The cars built during those first 3 months are identified by collectors as 1964 1/2 although they are all registered as 1965 cars. 

Production resumed in September 1964 with a series of upgrades including new engine options, minor cosmetic changes, and generators replaced by alternators. These are regarded as 1965 models. 

Hope that helps. 

This thread made me listen a bit more intently to my Large Advents yesterday and there is a quality that is not present in most current-era speakers; different bass instruments appear to emanate from different depths within the general area of the speaker. It is not image depth or soundstage depth per se but it is a distinct quality. Where the speakers fall down a bit is in midrange and treble continuity. Male voices sound a bit too chesty and female voices tend to sound a bit disembodied. The treble at the very highest frequencies sound a bit shrill and tizzy. It is a very enjoyable speaker but yes, it is no longer high-end. Perhaps it never was. 
I watched that weird movie with Tom Cruise and Penelope Cruz last night, Vanilla Sky. Pretty sure Tom is seen driving a '69 Mustang repeatedly in the beginning stages of the movie. To me it is a classic just as something my dad advised me when I was a teenager-gray wool slacks with a medium lapeled blue blazer is always a classic.