Not really sure about this one... Reminds me of seal buttons. Some were used to be offered as a promise to the beloved one (at least in France) during the 18th century for instance.
Here are some examples :
Just flip them horizontally to get the actual print...
What makes me think of a seal button for yours is the result when you flip it horizontally : (which should produce the resulted print when the button would be used as a seal)
I might be wrong but I think I can read the letter "K".
Obviously, your button would not serve the same purpose as the other ones on the first pics. However, it may have been a seal button for another reason. This I can't figure... Livery?? Specific uniform?