Most modern conventional typewriters until 1960 worked on the "front
strike" principle. This refers to the printing mechanism. The printing
letters are mounted on the ends of rods called "type bars." Front-striking
type bars rest horizontally and swing forward to strike the roller at the
With that in mind, here is a rule of thumb to distinguish conventional from unconventional typewriters.
The 4-row, front-strike format was established by Underwood
in 1895. It was used on almost all manual and electric typewriters until
IBM changed the industry with its "golf ball" Selectric in 1960.
Collectors generally prefer unconventional typewriters for their
collections, though early or fine examples of some conventional machines
may also be collectible. Most collectible typewriters date from 1874 to
about 1915. Only those 100 or more years old are genuine "antiques."