October 22, 1913 was when the Northern Pacific Rules and Specifications Governing Uniforming of Employes was to go into effect, introducing the new NP buttons.
Interestingly, in 1913, NP employee uniforms were to be outfitted with black (hard) rubber 4-hole buttons, over which
1913: Hard Rubber on Uniform is the second installment of the 4-part Northern Pacific series in the WRBA Button Aerogrammes. Stay tuned for more.
The above is based on the National Button Society's Classification System.
WRBA Button Album encourages discussions across various button groups, in-person or online. Please reach out to us with additional information or suggestions.