The iconic 5 pound orange Queen Victoria postage stamp started out life originally as a telegraph stamp. The part of the die that said "telegraphs" was milled out and a slug saying "postage" was inserted. The 5 pound telegraph stamp was found necessary to pay for the enormously high rates for overseas telegrams in the late 1870's when it was first issued.
These German "Reichspost" definitives (1900) have two-line markings of "Berlin C." and "T.A.2." which appears to be Telegraphenamt 2/telegraph office 2 in central Berlin. Don't know if this marking indicates postal or telegraph/revenue usage of the stamps.