I was thrilled to find a facsimile of Grierson’s Linguistic Survey of India in the university library. Plans to go and see the original at the SOAS library are afoot, but till then I’m happy with this one. I have borrowed the second volume of the fifth part; this is the one that covers the Kaithi script.
The handwriting samples exhibit some deal of regional variation in the shapes of letters, based on the dialect that is being written. Most of the changes in shape look like a function of speed, but some not so much; see the /ṇ/ in the second column of the first row, for instance. The following table (click on the image for larger size) from the book shows the Kaithi alphabet as written by Tirhuti, Bhojpuri and Magahi scribes.
Handwriting Samples
There are handwriting samples that have a continuous headline, and those without; with word spaces, a dash for a word space or without any at all. The first two samples are in the Maithili dialect of Bihari from Darbhanga and Purnea district respectively; next is the Magahi dialect from Patna; and finally, the last two are the Bhojpuri dialect from southern Saran and eastern Gorakhpur.
Its a Nerd’s Life! 
Satwik Gade January 10, 2012
Brilliant!!! Awesome. But this is like the first sip of iced scotch, I will be jittery until I see the whole bottle through! Bartender! Keep ’em coming!
makeishura March 15, 2012
Amazing grace and fluidity! And the matras in the second sample! There should be a font like that
Deep December 14, 2013
Great work Pooja. I sometimes hear from my mother that when she was young, she used to write in Kaithi. I will share this article with her. thanks for bringing it here.
Bikas October 10, 2014
this sanskritisation thing has ruined the local script as well as the languages .
today state language of bihar is Hindi and script is devnagrik , both have no history in bihar prior to 1900.