Judging by Stevie's hair -- brown, center part, bangs that have grown out to about her cheekbones -- this is around the time they were recording and preparing to release
Fleetwood Mac. Lindsey had transitioned from the brushed-out long hair to a small fro at that point, but he still had a mustache and no beard (as seen in this pic:
http://www.superseventies.com/oaaa/o...etwoodmac2.jpg) so his hair looks about right for that time too. This would be around the time that they were pinning $100 bills to their walls, so she would have had enough money for a fancy dress, and I think Lindsey's big collar is a look that was popular around that time, right? "Landslide" would have been written already, so the caption claiming that's what they're singing could be right, as would HejiraNYC's assessment. And then Lindsey is playing without a pick, and the position of his fingers on the fretboard looks very Lindsey, and I'm pretty sure we've seen Stevie sitting in that position while singing before -- the way she's leaning forward with her arms across her lap and her hands hanging down looks super familiar to me, although I can't call to mind the photo I would have seen it in before. So even though my initial reaction was that this was fake, it would have to be a
really good fake by some
really attentive fans, because all the details down to the body language point to this being a real photo of Stevie and Lindsey from 1975.