2.1.272 Part 1 Section 17.8.3.13, panose1 (Panose-1 Typeface Classification Number)

a.   The standard states that when a font is unavailable, the panose1 element shall not be modified.

Word does not roundtrip the panose1 value for fonts not installed on the system.

b.   The standard states that when a font is unavailable the panose1 element shall not be modified.

Word can modify the panose1 element of an unavailable font if a font with the same name has been loaded before in the same Word instance.