Each of these is one half of a stereograph photo.
Beautiful girls of the mountain-top town, S. Guiliano -
view S.E. to mediaeval castle, Sicily, ca. 1906
Fifth Ave. and the Waldorf, New York City, 1909
Getting her hair banged, ca. 1900
[cue sexual harassment lawsuit in 3...2...1]
Hat and clothes market in the Jewish quarter, Warsaw, Poland, 1919
Inside a cotton mill at Malaga - spooling room and girl employees, Spain, ca. 1908
Source: Library of Congress