My wife and I saw the group again yesterday near the Lincoln. Unfortunately, we did not have the time to pull over and go over all the field marks such as bill size. We had already burned some time looking at a small flock of 6 Goldfinches in winter plumage in the neighborhood, so we could not risk being too late for work. I will try to run over there today and get a better look.
 
Among other gulls, I saw a Lesser Black-backed Gull (yellow legs being the key ID feature) near DD 933 at the Washington Navy Yard. Gulls of various types (Herring, Great Black-backed, Ring-billed, sometimes Laughing and Less Black-backed" like to sun themselves on the piers near DD 933. Since the piers are roped off, the birds have almost no fear of humans, which allows one to get very close for excellent views. 
 
It is possible for the general public to gain access to the Navy Yard too see DD 933 and the Navy Museum. Information about public access can be found on this web site:
 
http://www.history.navy.mil/branches/nhcorg8.htm
 
John Sherwood
Washington, DC