Unusual Coloured Duck

[Derickp]

This Duck photo was taken about 150 yards out on Scaling. Looking through Scope it had Grey Head & down the neck to just above shoulders. It had a Black eye stripe. Lovat Green coloured Bill turned slightly down at end, and shoulders were a similar colour to bill. Brown flecked wings with more concentrated brown near primaries. Prominent white on upper tail area. Light buff toward rear flanks. I just simply cannot match it to any photos I have.  I.D would be appreciated.