NavList:

While looking for something unrelated, I came across an article on time balls from the Cincinnati perspective. It's rather lengthy and interesting, if you can forgive a few slips, e.g., "Global time, known as Greenwich Mean Time (GMT), was not used as a worldwide standard until 1954 and is known as sidereal (from a Latin word for star) time based on stellar observations, not solar time."

http://www.voamuseum.org/media/1355/how_time_balls_worked.pdf

It refers to a War Department Signal Service document on time balls, but the link takes me to a something on meteorology. The correct document:

US War Dept, "Information Relative to the Construction and Maintenance of Time-Balls," 1881.

"The importance to the Signal Service of the general distribution of accurate time for the use of its voluntary and regular observers throughout the country has induced the Chief Signal Officer to heartily co-operate in the maintenance of time-balls. In order to satisfactorily answer the numerous inquiries addressed to him as to the best methods of construction, &c, he has caused the accompanying Circular of Information to be compiled."

It's not really a "mil spec" on time balls, but rather a collection of replies from various time ball operators on their thoughts regarding good practice. One item the War Department requested was how to protect the roof from the "concussion" of the falling ball.

https://books.google.com/books?id=GCBJAQAAIAAJ

--
Paul Hirose
sofajpl.com