Lesser Black-backed Gull NU6 6cy, April 22 2002, Missouriweg - ECT, Maasvlakte, the Netherlands (51.59N,04.02E). 

An adult ringed, left orange with a white code NU6. Ringed as pullus at the nest, July 11 1997. Although these rings are rather new, the white code may be hard to read. There is a mirror on both p9 and p10 and the shape of the p10-mirror can be seen in the image as the  primary is slightly displaced.