It appears to be a British or Commonwealth Forces chaplains badge, I say "appears to be" because I don't know much about chaplains insignia and I can't find one online in green. Pattern wise it's right though.... I'm a little suspicious of the loop at the top, but that may have been added later. Are you sure it's actually gold and not plated?
It's a cool badge, and it should be somewhat dateable by the crown.. a "kings crown" would date it from 1901 - 1952, and a "queens crown" from 1952 - now.... I don't however, know the difference between the crowns.... Maybe one of our English members could help with that