The front of the badge has a light bronze coloured petina. The reverse is brighter. While I have not cleaned the cap badge, I’d suggest a light polish would restore it to its orignal goldy colour.
In my opinion, this is a pin backed version of the 1923 pattern staff officers’ badge NOT a badge that was subsequently brooched. It reminds me of the pin backed style Drong Átha Cliah cap badges worn by members of the Irish Voluteers.
This is a great early Irish National army cap badge that would be a centre piece of an Irish collection.