Okay, searches were drawing blanks on the button until I realised I hadn’t seen that crown before. Looks like it’s not British, Kiwi or Australian, but maybe Imperial German Navy???
Only words I can make out are:
Bottom of button: A&S with a 5-pointed star each side
Top: K. D________rine
And as I typed that last line, it clicked to try DeutschMarine and TaaDaaaa! a direct hit, so to speak.
1888 German Imperial Navy.