Before we start as few words on proportional
spacing. It was invented in 1941 and was included
on the IBM Selectric 1 that was put on the market in
1961. ( For a source look up Wikipedia Selectric 1
If you are given two documents and wish to separate the computer
generated one from the typewriter generated one almost all the
characters will be identical. But there two
exceptions. They are the double quote and the
single quote characters.
Computers store font information in memory and use two
different symbols for opening a double quote and closing a double
quote. They also use two different symbols
for opening a single quote and closing a single
quote. The symbol used to close a single
quote is also used as an apostrophe.
Here is an example of computer generated quotes.
Typewriters limit the number of characters they can print so they
use one character for both open and closing double
quotes. They also use one character for the
opening and closing single quotes and as above they use this
character for the apostrophe. The symbols they use
are either 2 vertical lines or one vertical line.
This is shown in the following photo
Also important is the space required for the apostrophe is larger in
typewriter text than in computer text.
A close look at the so called "Killian letter" reviles that the
apostrophe used is different in the two letters
compared. It is vertical in one letter and
slanted in the other letter.
here is a link to the killian letter
Clearly the vertical apostrophe is a typewriter symbol and the other
apostrophe is a computer symbol. This is difficult to
see but it is possible with a magnifying glass.
As for the raised th in the text it was possible to get custom
"character sets on the IBM Selectric 1 that had custom
And here is another view of computer generated fonts.