In a discussion on thegearpage.net, it is confirmed through images that guitarist John McLaughlin uses a 1966 Fender Duo-Sonic II Electric Guitar. The thread also highlights that the instrument played by McLaughlin is the shorter scale version.

In the video for "Soranin" by Asian Kung-Fu Generation, Gotoh Masafumi can be seen using a 1960's Fender Duo Sonic in Daphne Blue w/ a Red Tortoise color pickguard.

The guitar can be clearly identified at 1:59 of the mentioned video.

From The Line of Best Fit, 12 June 2012: "Well, I have a 1966 Fender Duo-Sonic in Daphne Blue. I was playing a show with John and Jehn in France, in their hometown. We had a few days before this show, and John took me to this guitar shop where he’d bought a lot of his instruments. He knew the guy, and he said he’d lend me this guitar for two days. He didn’t tell me how much it was. So I sat round the fireplace in France for two days before the show just playing this guitar, and I completely fell in love with it. I gave it back, and I came back to the UK. But I couldn’t stop thinking about this guitar.

By then he’d told me the price, and I just thought, no way. But I did everything I could in my power to get hold of this guitar, and I ended up picking it up from a French lorry driver on an industrial estate in east London. He held up all the traffic. I’m in the corner of this industrial park looking out for a specific French lorry, getting some weird looks. But eventually he came, stopped all the traffic coming off this A road, got out of his cab and gave me this guitar and off he went."

From Wikipedia entry for Fender Duo-Sonic: "Third version – Duo-Sonic II (1964–1968) In 1964 the Duo-Sonic was redesigned based on the Fender Mustang that had recently been added to the student model line but without the vibrato tail-piece. The student guitars now all featured larger and slightly offset bodies, necks with larger headstocks and rosewood fingerboards and plastic pickguards with the volume and tone controls mounted on a separate metal plate. Pickup selection was moved above the pickups on both the Duo-Sonic and the Mustang and utilized two 3-position on-off-on switches that allowed for in and out-of-phase sounds. The pickups were also reverse-wound/reverse-polarity, which made them into a functional humbucker when both pickups were used simultaneously. Also added in this redesign was the option of a 24 inch scale neck in addition to the 22.5 inch scale. This re-designed model was renamed Duo-Sonic II although decals with and without the II designation were used occasionally. In addition to white, Daphne Blue and Dakota Red colors added.

The Duo-Sonic lasted until 1969 when it was dropped most likely because the Mustang with its tremolo tail piece was far more popular.

The Duo-Sonic I and II are both considered rare and have displayed growing collector value. The Duo-Sonic II in particular is often seen as a desirable alternative to the more popular Mustang, since it lacks the difficult-to-maintain tremolo bridge."