Keystone Telephone Co. of Philadelphia (Philadelphia) 

Sections of digitized microfilms (1st filming 1908-1949)

For intellectual property law reasons accessible only on the web from the European Union legal area and from the ZBW reading room.

Total number of images: 29

Sections of digitized microfilms (2nd filming 1950-1960)

For intellectual property law reasons accessible only from ZBW reading room.