When opening the Google Font repo version of this font (1.003) on Windows 7, all characters are displayed using a fallback font (Arial I guess). On OSX this works fine.

Version 1.001 of this font (as found on e.g. http://www.fontsquirrel.com/fonts/amatic) works fine on Windows, but might have other issues

Re-generating the TTF using FontForge fixes the problem.