Good Afternoon, Dr. Bob and Old Top;
I don't get out to the Department of the Atlantic near as much as I would like -- and although this was a business trip, it would have been nice to be able to visit a military museum, armory, etc. Sadly, not much like that exists in Manhattan anymore.
As for the summer whites, I don't have sufficient information on the post 1903 timeframe to hand here at work, and my library at home doesn't go much beyond that timeframe either with regard to the Army. Now, if we're talking about the Marine Corps, I can state that the Marines had summer whites from 1875 up to and including 1912 (the limit of the uniform specifications I have handy) and likely continued without interruption right up to the present day.
I have the honor to remain,
Your Obedient Servant,
Bvt. Captain Malachi Thorne