Lesser Black-backed Gull NX5 6cy, April 22 2002, Missouriweg - ECT, Maasvlakte, the Netherlands (51.59N,04.02E). 

An adult ringed, left orange with a white code NX5. This bird was ringed as pullus at the nest, July 12 1997. The 5 in the code very much resembles a 6; although these rings are pretty new, the code may be hard to read in some cases.