IBM Selectric
History and Basic Info
The IBM Selectric typewriter was introduced on the 31st of July, 1961. This typewriter is equipped with a golfball sized type element instead of a type basket so that typefaces can be easily interchanged. The series started with the IBM Selectric (It's original designation does not include a I, but for consistency's sake, people usually call it the "IBM Selectric I" or just "Selectric I") , which evolved into the IBM Selectric II, and finally the IBM Selectric III.
The Typeball
The IBM Selectric's typeball gives it some major advantages over a traditional typewriter. Typeballs can be swapped out quickly allowing for multiple typefaces on one machine, the selecting mechanism is much faster than a traditional typewriter, and some machines are even equipped with IBM's "Dual Pitch" option which allows the machine to type in both 10 cpi (Pica) and 12 cpi (elite).