New Zealand WW2 era 22mm Bakelite Button Royal NZ Air Froce
A black 22mm Bakelite "War Economy" button to the Royal New Zealand Air Force.
I think this is a Australian manufactured button, as you certainly find quantities of their button's in this style and with the "MP" logo to back.
Light wear to front, with a few scuffs.
To back, the integrated shank is in good condition, and as mentioned a "MP" mark or logo stamped to back.