Larus fuscus fuscus 3cy C6XM, July 16 2003, Tampere, Finland (61.33N 24.59E).

C6XM was ringed in Hauho, Finland; ringed as pullus on June 30 2001 by Risto Juvaste.
Ring records at Tampere landfill:
2003-07-16.

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.

C6XM was ringed in Finland, now in 3cy. This 3cy fuscus has arrested primary moult prior to northbound migration: there is a clear division in the visible outer primaries between P7 and P8. The three outer primaries (P8-P10) are bleached brown and P10 has only a very small mirror. The other visible primaries, P5-P7, are much darker with small white tips.
Note the limited dark markings on the bill and the dark iris; indications for 3cy birds.