(2 images) Larus fuscus fuscus 3cy C6XP, July 15 2003, Tampere, Finland (61.33N 24.59E).

C6XP was ringed in Hauho, Finland; ringed as pullus on June 30 2001 by Risto Juvaste.
Ring records at Tampere landfill:
2003-05-29, 2003-05-30, 2003-05-31, 2003-06-01, 2003-06-03, 2003-06-04, 2003-06-14, 2003-06-16, 2003-06-17, 2003-06-18, 2003-06-20, 2003-06-22, 2003-06-28, 2003-07-05, 2003-07-15, 2003-07-06, 2003-07-16, 2003-07-20.

Larus fuscus fuscus in 2cy often returns with completely replaced primaries and secondaries. In 3cy, fuscus more often shows a clear division between fresh inner primaries and older outer primaries, the inner primaries often showing neat white tips and the outer primaries often second generation-like with rounded tips and paler bleached brown. The arrested moult in the primaries is often reflected in the secondaries and (to a less extend) in the tail-feathers as well. The older tail-feathers (often R5 is older) still show a broad dark sub-terminal band.
3cy fuscus often have some black markings on the bill, which is otherwise much adult-like, with a clear red gonydeal spot. The colour of the naked parts are adult-like as well. 
The scapulars in 3cy are often completely adult-like, lacking internal patterns; plain blackish grey with a mahogany hue on the older feathers. Most wing-coverts and tertials are adult-like blackish grey as well, but often 3cy birds show some very bleached pale brown wing-coverts, normally in the greater covert bar and in the upper rows of the lesser coverts. These bleached wing-coverts accentuate the jumpy sequence in the last wing-covert moult cycles, as there is often no clear pattern in location of these bleached feathers. Head and body feathers normally are snow-white by July.

C6XP was ringed in Finland, now in 3cy. This 3cy fuscus has arrested the primary moult prior to northbound migration: there is a clear division in the visible outer primaries between P8 and P9. The two outer primaries P9-P10 are paler brown second generation, P10 with a small but obvious mirror. The other visible primaries, P3-P8, are much darker, glossy black with relatively large and fresh white tips (adult-like primaries) especially on those primaries protected by the tertials; and they are the next generation flight feathers.
The almost completely white tail has some black markings on the inner rectrices. There are some dark markings on the bill and the speckling on the iris are indications for 3cy birds.