IBM Typewriter - Model B Executive

IBM Model B - Executive

I've just picked up this beast of a machine and have been looking into its history. Something I just found out was that the Executive version of the Model B was fitted with proportional spacing, this turns the familiar typewriter style printing into something resembling a real printed document. The following extract from Wikipedia shows the significance of this feature in the 1940's.
According to Darren Wershler-Henry,

In 1944, IBM launched the Executive, a proportionally spaced typewriter. Characters on the Executive typewriter occupied between two and five units per grid cell, depending on the width of the letter. Beeching relates an anecdote that demonstrates the significance of this achievement. The proportionally spaced typewriter immediately leaped to the apex of the world bureaucracy and administrative culture when President Roosevelt was presented with the first machine off the line. The Armistice documents that ended World War Two were typed on an IBM, as was the original United Nations Charter. To a world accustomed to monospaced typewritten documents, a page of typewriting produced with an Executive...was indistinguishable from a page of typeset text. Prime Minister Churchill allegedly responded to Roosevelt that "although he realized their correspondence was very important, there was absolutely no need to have it printed."^[2]