WW2 US Navy Wool Thermal

World War 2 US Navy issued Wool Thermal undershirt pullover uniform Vintage 1940's Gray knit wool Fresh out of the attic, have not tried to clean it. Imperfect as shown in photos, but nice condition considering it's literally been through the war. This was my Grandfather's and he served on the U.S.S. Calvert. My guess is size M