Very interesting picture... I think it's rather his 1976-1978 drumkit since it is a Premier, not a Gretsch or a Pearl (he had those later I believe, but I'm not a drummer, so I'm not a specialist).
Phil had a different Premier kit on the Duke tour (check out the Lyceum concert video) that has a lighter natural birch finish. His Lamb/Trick Tour kit was a darker, mahogany finish.