It looks like it a chinese round , probably from the Heilongjiang North Tool Factory in Mudanjiang, Peoples Republic of China (code 121) manufactured in 1975 I would treat it as corrosive to be safe.
This particular round was manufactured in July of 1975, by Wang Qiang Zhang, shortly after the birth of his daughter, Wang Jing. The rice crop had been poor that year, and Wang Qiang was disappointed with the distribution of food in his village of 300 factory workers. Despite virtuos tales of sacrifice by party leaders, Wang Qiang had seen with his own eyes how party favorites were alloted more of everything. In an a move of quiet revolution, Wang Qiang mixed corrosive primers into the production line-up, imagining that PRC military rifles would rust out earlier than hoped, giving future generations the oppurtunity to overthrow their new leaders, that seemed more equal than others.
Little did he know that factory bosses were informed of his treachery, and marked the crates for export only. In Chinese characters the crates read:huĂ idĂ n
Literaly: Bad Egg
This indicated the ammo was corrosive, and was an inside joke about the acrid smell. When the time was right, they shipped the ammunition to their western enemies, knowing well that it would be misrepresented by various dealers here as non-corrosive, and destroy our rifles before the coming East/West war. A death of a thousand cuts is still a death.
Little did they know, in Canada, we had a secret antidote: the worlds greatest supply of fresh water.
True story. Why would I make it up?