Some additional information on Placards. I have been doing research for an article on placards. My former career was teaching Hazmat so I had an interest.
The earliest placards I could find were from 1903. The earliest regulations I could find were produced in 1908 by the ARA.
I posted photos of some of the placards and pages from the 1908 regs in a folder called Paul's Placards. I have data and placards from 1903 until present day but they are in storage. Some day I will dig them out and get the article written

Paul Deis
D&P Mountain Railroad
curlyp2@...
http://web.mac.com/curlyp