Age: This is one of our four-year gulls. Almost everything looks okay for an adult, but the dull bill pattern with black near the tip, and darker greater primary coverts (just below the drooping white secondaries at the base of the outermost primaries) suggest a subadult. Here, subadult means a bird that's mostly adult, but with one or two imperfections. This is a vague term for what could be a very advanced 3rd cycle type, 4th cycle, or perhaps an older bird with some retained "subadult" features.
Identification: Given the location, let's start with the expected pink-legged taxa: Western and Glaucous-winged Gull. The gray upperparts look a tad darker than a typical Glaucous-winged and slightly flatter and paler than Western. Also, the dusky gray primaries are intermediate between the black on Western and pale to medium gray of Glaucous-winged. You may already be on to where this is going. Intermediate individuals such as our October Quiz gull are freely assigned to the hybrid population of this region: Glaucous-winged x Western, or Olympic Gull. They often have more bulbous-tipped bills than this one, but we might attribute this to our bird being a slighter female. The smudgy head, neck and breast markings are expected on both Glaucous-winged Gull and Olympic Gulls, and to a much lesser extent, on Western Gulls (subadults).
It bears mentioning that birds with this amount of pigment on the primaries are routinely identified as pure Glaucous-winged Gulls in far northeast Asia. From southern Alaska down to central California, Glaucous-wingeds with this degree of pigment on the primaries are often suspected of having either Herring or Western influence. However, there are apparent pure Glaucous-winged Gulls with darker primaries matching our bird. Those birds should score perfectly in other areas such as wingtip pattern, gray upperpart coloration, eye color, orbital color and bill color/pattern.