The two most-common collectible typewriters are the Folding
Corona and Oliver. After those come the single-element
Blickensderfers and Hammonds,
the upstrike Remingtons, the upstrike Smith
Premiers and Caligraphs with double keyboard
and the thrust-action Wellington (also sold as Empire
and Adler). The No. 1 models of the Oliver, Blickensderfer, Hammond and
Caligraph are not so common, and have much greater value than their later
counterparts.
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There were many other typewriters which were produced in great numbers,
and are also easily available. Fortunately, those are the machines which
best illustrate the development of the typewriter to its modern state. They
are common, because they were successful, and, therefore, produced in great
numbers. Rare machines are those whose designs did not well serve their
users, and thus failed in the marketplace. These often represent "dead
ends" in the evolution of typewriters.