As you can see from the original card, these were made in occupied Germany. Germany was occupied by the Allies from 1945 until 1949, so these buttons were made during that time period, and were made somewhere within the US Zone.
I always recommend caution in exposing old buttons to water. These buttons are as close to pristine as a vintage button can get - you may see some aging of the foil around the edges of some of the buttons, to be expected, given their age, even as they are coming off the original cards to which they were sewn in the 1940's. However, I have no way of knowing what might happen to the foiling if the button is placed in water, so I recommend keeping them as dry as possible.
Have any questions? Contact the shop owner.