said there were IBM machines capable of producing the spacing, and a customized key — the likes of which he said were not unusual — for creating the superscript th. Thomas W. Phinney II, program manager for fonts at Adobe Systems, responded to Glennon's statement by saying that the memos could not have been produced with either the IBM Executive or IBM Selectric Composer, which had been suggested as possibilities, due to differences in letter width and spacing. Phinney says that each time a typeface was redeveloped for mechanical technologies with different width factors, the width and designs are altered, which is why even if Press Roman had been intended to look like Times Roman, the result is significantly different. Phinney suggests that the real typist prevented Word from auto-formatting "th" in superscript by typing and deleting a space in some cases but in other cases did not use the space or left it in the document. Phinney's analysis was based on the fact that the typography of the Killian documents could be closely matched with a modern personal computer and printer using Microsoft Word with the default font (Times New Roman) and other settings. Therefore, the equipment with which the Killian documents were actually produced must have been capable of matching the typographical characteristics produced by this modern technology. As Phinney explained, the letterspacing of the Times New Roman font used by Microsoft Word with a modern personal computer and printer employs a system of 18 units relative to the letter height (em), with common characters being 5 to 17 units wide. (The technology allows even finer variability of character widths, but the 18 unit system was chosen for compatibility with the Linotype phototypesetting and earlier hot-metal versions of the font.) In contrast, the variability of character widths available on early 1970s typewriters using proportional letterspacing was more limited, due to the mechanical technology employed. The most sophisticated of these machines, the IBM Selectric Composer, used a system of 9 units relative to the letter height, in which all characters were 3 to 9 units wide. Less complex machines used fewer widths. Differences in individual character widths accumulate over the length of a line, so that comparatively small differences would become readily apparent. Because of the differing character widths employed, the letterspacing exhibited by the Killian documents (matching that produced by a modern computer and printer) could not have