1978, I think this predates the Superscope/Marantz dual deck by a year or two, it's certainly one of the first.
Interesting! Who made those Music Air? There was a similar Sony AFAIK but AFAICR this doesn't look like a direct clone..
I was trying to find some more information but the name is too generic, I did just find that 1001 Hi Fi beat me by two years finding the ad, there's some other cool dual decks on this page. https://1001hifi.blogspot.com/2016/07/unique-2-in1-audio-components.html