I'm planning to order a new top for my '25 Touring, Serial # 11830895
According to the encyclopedia, "Later 1925 tops had one rear window, as in the 1926-27 models."
Which top would be correct for my May 1925 built car, two windows or one?
May 1925 is your car, so that is later in '25 as the 1925 model year began Aug. 1924.
Your top needs a single rear window 16 3/4" x 7"