[XeTeX] Alternate Ξ glyphs in GFS Neohellenic

[BPJ]

Dear Greek-users on the list,

according to the type specimen[^1] there are three different Ξ glyphs in the OTF version of the font GFS Neohellenic[^2] but I can only access two of them -- of course not the one I want at this time, the one without vertical or diagonals!  Peeking inside the font with FontForge hasn't made me any wiser.  Does anyone know how to access them all?

TIA,

/bpj


[^1]: http://www.greekfontsociety.gr/images/NeoHellenic%20Specimen.pdf
[^2]: http://www.greekfontsociety.gr/GFS_NEOHELLENIC_OT.zip