Unknown portrait of George Thomas

Have not seen this portrait of George Thomas in the literature before. It seems based on a photograph. The picture hangs in the Army & Navy Club in DC and no date is given, no artist is credited. Have seen it often but decided to snap it at lunch yesterday using my crappy phonecam.

If you are planning on writing a George Thomas bio (possible theme: America's unknown hero), go get a better photo for your cover art.