I have a copy of “Transportation of Explosives and Other Dangerous Articles by Freight including Specifications for Shipping Containers”, issued 12/11/1922, effective 1/1/1923. Required by a 3/4/1921 amendment to the Transportation Act of 1920. This is a ICC publication of regulations [actually labelled as “Freight Tariff No.1”.
Article 700 is “Labels” and shows required placards [classic diamonds]; red for inflammable liquids & gases, yellow for inflammable solids, white for acids & corrosives, white with red letters for poison gases and green for non-inflammable gases. These required on packaging.
Article 900 is required “Placarding of Cars”, but this has illustrations for explosives, poison gas, inflammable liquids and acids only. The last two are diamonds like the packaging, while the first two are rectangles.
So, 1/1/1923 is an official date for placards. I note colors noted above are currently used [e.g., yellow flammable solid]
So, did the diamond come for the law requiring these regs? Or perhaps from a prior Bureau of Explosives document? I have found articles that say railroads required labels for Dangerous Goods in 1910, but have yet to find any specifics on that.
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