Hmm seems weird although looks like that API is deprecated The following seem to work a treat though
http://finance.google.com/finance/info?client=ig&q=ASX%3aIPP
http://finance.google.com/finance/info?q=ASX%3aNST
Is IPP.AX the official way to express stock_ticker.exchange? and is AX the exchange code for the ASX?
