Possible 3cy Caspian Gull L. cachinnans at Tara dump, Tampere, SW Finland on 23.10.2010. First 4 fotos: Markku Kangasniemi
This obviously male called (was found by voice first, like many others earlier) and longcalled like a Caspian Gull.
Jizz and structure not really different from argentatus, however.

In flight still some brownish pattern on underwing (could be totally white on typical Caspians), head + bill jizz not different from HG L. argentatus. Primary pattern is not like typical Caspian should show: P10 not all-white, inner webs of outer prims look blackish, but overall pattern is more like HG or YLG type. Fotos: Hannu Koskinen

This photo shows well the upper handwing pattern. 6 black primaries (and a hint on p 4). Note the pattern on inner webs of primaries p10-p5. Looks blackish, but there are non black shades on inner webs.

A bit more black on right wing p10.

Another Gull to compare with: