The primaries on this bird are slightly darker than the rest of the upperparts and the tertials also have muddy centers.  However otherwise It seemed a pretty classic Glaucous - very large, bigger than any smithsonianus around, and the bill looks good for Glaucous. Perhaps a dark bird originally and for some reason the primaries/tertials have faded the least, or maybe it has some Herring genes?  

Here is a comparison of head and bill profile of this bird with adult Great Black-back and American Herring.