This picture was taken at Larson AFB in Feb 1960 and is the courtesy of Dick Vanallen
Dick stated that SAC modified the cabin door by putting the extra windows in. These helicopters were missile site support and when transporting the missile crews the extra windows in the door helped eliminate the closed, boxed in feeling the missile crew had riding in the cabin. Apparently only a very few were modified. Dick stated there is one locked up in a building in Alaska however when he was there he was unable to see it and find out the tail number.