Based on the reports it sounds to me like the seventh was actually remodeled twice. Before the 1938 they reduced the size of the green and added a new bunker. And then the next year they relocated the green a bit further up the hill and surrounded it with bunkers. I believe Horton Smith is credited with that idea.
From the March 27, 1939 Augusta Chronicle (Tom Wall):
"During his practice round yesterday, Armour took time out to note the change made on the seventh green. 'with that change the hole is far more interesting than ever before,' he was heard to say.
His remarks brought back memories of the late Dr. Alister McKenzie's appraisal of the hole when approached by Jones, who the architect designed the Augusta National. Dr. McKenzie agreed that a change was in order at the seventh but said he was not sure just what sort of change it should be.
'Just we wait until some golfer offers a new idea,' the architect advised. Jones concurred."
From the July 18, 1938 AC (OB Keeler) describing the first change. The last part is kind of ironic:
"The seventh hole, 340 yards from the championship tee, and regarded as rather too simple a problem, with its ample kidney-shaped green, and its short range, of the drive-and-kick variety, the kick frequently being of no more than 50 or 60 yards, and at times, for Jimmy Thomson or Sam Snead or Lwason Little, dwindling to a mere chip.
The baronial hunch, which is being carried out, is to operated on the kidney, cutting off one end of it at the left, this diminishing its area and further complicating an approach from that side by a neat little bunker, leaving the larger 'picture bunker' where it is back of the green, where it sets off the picture and incidentally punishes a too-enthusiastic bang from the front.
I confess that when I heard that changes were contemplated at the Augusta National, my reaction was exactly similar to that ascribed to Big Bob Jones, who is said to have inquired with an emphasis not wholly in keeping with expressions in a great family newspaper what the thunder they hoped to do to improve a course already so near perfect."