They are prewar Type T from what I see. I will check the reference. I hope you are using something more modern.
The T was made throught 1925 to 1938 and rated at 100 watts. The 1925 version had a light socket adapter.The 1938 had a two prong plug. It is listed in both cats so I am guessing on production years . I can't tell you when it stopped. Unless the year is on the case.
The service manuals have the charts. The blue hardcover runs about 50 now for postwar service. To anwer the question U is the common, A etc is normally the voltage across to u. Each transformer can be different. Some are variable to run the train the others are fixed for accessories like lights and switches and decouplers. Each transformer has it's own chart.
I looked around and I have only a Prewar N at 50 watts and this American Flyer.