The writeshield screen that I have installed for my little M (M1300 VA) is actually one for a Toshiba 35XX.
I believe the Toshiba tablets do not have glass screens but a plastic/polymer mix.
The writeshield should work on the M1400 but you might want to call Motion and http://www.pocketpctechs.com
to get the latest information.
I have been very happy with the Writeshield on my little m.