I was most impressed with Hans Kettenburg's fine article on Telegraph Signs in the August, 1985 issue (see p. 21). In as much as he asked for additional information, I'd like to offer the following:

Western Union was to the telegraph business what American Telephone and Telegraph Company was to the telephone industry. Therefore, it was thought by many a logical step to merge the two. With that in mind, AT&T acquired 30% of Western Union stock and on December 20, 1910, took over operation of the telegraph giant naming the president of AT&T, Theodore N. Vail, to head both organizations.

Immediate steps were taken to merge the operations. Enter: advertising signs associating the two utilities. The illustration on Fig. 1 of Hans' article (see Fig. 1 below) was to appear in several forms, used both in signs and in media advertising.

The merger provided revolutionary benefits to both the companies involved and to the using public. Costs were reduced and at last one could place and receive telegrams via his/her telephone.

There were, however, in our government, powerful opponents who, by 1913, were exerting great pressure to dissolve the merger. They were to prevail and on March 19, 1914, the union was dissolved.

So, as we see, the sign in Fig. 1 was no doubt introduced in 1911. I think it's a fair conclusion that the sign in Fig. 10 of Hans' article (see Fig. 2 below) came in this same period. The candlestick telephone illustrated a 1910 introduction of the Bell System and most assuredly would not have been used had there not been an association between the companies. This instrument was to be phased out beginning in 1919 by dial model candlesticks and in 1928 by the cradle or desk set.

The practice of displaying signs associating both the telephone and telegraph begun with the merger was to continue for many years but, to my knowledge, no mention of a Bell Telephone Company name is made on signs after 1914. This was true with Postal Telegraph and other lesser known companies.

Trusting this will fill in a few gaps for your sign savers.