"Mate, are you fair dinkum?" - Kind Sir, are you telling me the truth, the whole truth and nothing but the truth?
"Mate, I'm fair dinkum, bloody oath I am" - Why of course!!
"He's a fair dinkum drongo" - He is honestly quite a fool who isn't too bright and gets nothing right. The fair dinkum adds the honestly part to the translation, the rest comes from drongo.
"You have to let him know you're fair dinkum" - You have to let him know you are bona fide.
"Fair dinkum?" - No shit?
Aussie slang heres a post to help you understand what Fair dinkum is http://www.australianbeers.com/culture/fairdinkum.htm

enjoy you can also use it
