Age: The plain wing coverts, admixture of adult-like gray scapulars, single adult-like upper tertial and rounded primary tips all suggest a 2nd cycle type large gull.
Identification: The smudgy head, neck and breast appearance is reminiscent of Glaucous-winged Gull. The "muddy" plumage aspect to the upperparts is as if the bird was powdered with soot. Retaining a largely dark bill into 2nd cycle is also quite common for many Glaucous-wingeds. The only feature on this bird that raises some suspicion as to whether it may be a "pure" Glaucous-winged, is the paling iris. Most Glaucous-wingeds retain a dark eye, but some exceptional birds take on a pale eye (usually as they age, and not quite this young).
It helps to know that this bird was photographed in Grays Harbor, Washington. December. There is a large chance of some Western Gull genes at play, with a smaller chance of Herring Gull involvement. The very dark primaries may be viewed by some as a blocker for Glaucous-winged, but I don't see them as a problem for a bird with such closely matching tertials and greater coverts.
For what it's worth, here's what would be "safely" identified as a "classic" 2nd cycle Glaucous-winged. Seattle, Washington. January.
At any rate, we will settle for Glaucous-winged Gull for our July Quiz, with the unverifiable chance of some outside influence.