The AAT `ankr` anchor point table is an auxiliary table for `kerx`, used to store anchor overrides in case the glyph itself does not supply the needed anchors as control points. Among the fonts that come pre-installed with MacOS 10.12.6, `ankr` is used by a handful of non-Latin fonts such as “Myanmar MN”, “Devanagari Sangam MN”, and “Arial HB”. https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6ankr.html