One of the best collections is that at Hillwood Museum in Washington, D.C.,
containing the material obtained by Marjorie Merriweather Post. She purchased
quite extensively during her stay in Moscow in the late 1930s (while her
husband was FDR's ambassador to the Soviet Union) and in subsequent years she
continued collecting all manner of Russian objects, including imperial coins
and medals.
The Hillwood Museum is at 4155 Linnean Avenue, N.W., Washington D.C. 20008,
tel. (202) 686-8500. They could no doubt lead you to other related
collections.