Kavan Ratnatunga writes:

This talk presents ongoing research into the use of letterforms as a means of security for citizens and governments alike, thwarting forgery inplain sight and in secret. Some strategies have relied on high-profile collaborations, and others on home-grown cunning. Interwoven is a story of warand peace, technology, culture and economics. The narrative will focus on American banknotes from the Colonial period to the present day, withadditional examples of government permits and lottery tickets.

Kavan adds:

To watch the video, see:
Tobias Frere-Jones - In Letters We Trust - btconfBER2015(https://www.youtube.com/watch?v=dfbC_r76V1o)

For more information on the British Ceylon Colombo - Pounds Sterling, see this page from his web site:
British Ceylon Colombo - Pounds Sterling - 1850-1855(http://notes.lakdiva.org/british/psd/1850_gtgc_sterling.html)