Proofs ?
Most foreign countries require that all weapons be proofed by a government proof house. Different proofs for different guns and powders. [black and modern powders]
"Nitro" [or just "N"] is used for the modern powders [nitro-cellulose] which replaced the old black powders.
These tests varied over time..and the requirements changed. This subject is complex and complete books have been devoted to it.
If I can find it, I will post the name/publisher of one I use.
Orv Reichert
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