I acquired a copy of Dian ma Xin bian (電碼新編), a Chinese telegraph codebook, and added its images at
電碼――中国の文字コード (in Japanese) and
Chinese Telegraph Code (CTC),or A Brief History of Chinese Character Code (CCC) (abridged English version of the above).
The seller's website dated this as "1912", but, as expected, the book had nothing to support this dating. I think this copy was from the late 1930s.
