That's not from 1960!
That's from June 1909!
I should have remembered that, at various times (normally during peace time), arsenals would stamp not only the production year, but also the production month on the cases.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.