It was on the cover of a bootleg from 7 March 1970, in Montreux. There's a possibility that that's wrong, but I've seen other pictures of him in that shirt that all say they're from the same time/place.
Thanks for all of those great scans, Otto! I'm pitifully lacking in Jonesy pictures.
That one is miraculously sexy.
I see my favourite picture of him hasn't been posted yet! Well, must get to remedying that: