If you're talking Aussie coins, you need a 'Macdonald' - Greg Macdonald. My copy is a bit out of date, but I presume he's still going. In the 10th edition (Nov 2002), he gives mintage figures of 2,184,000 in total for Sov's (be aware that there are concurrent Shield and St George reverses running from 1871 to 1887). For this coin he gives the following values; Fine:$200 AUS, VF:350, EF:1500, aUNC:1500, Unc: 5500, Choice Unc:8000, Gem:11,000, Proof:50,000 1871 is the first coin of the series and in VF (which yours might be) it is the 3rd rarest of the sequence. I have some experience of the market in Oz - I used to get a load of stuff sent over 10 years ago or so, interest in the 'old stuff' has always been high because so little of it survives. It would seem that in the intervening eight years since I last looked, Aussie collectors have heated the market up quite a bit. Flog it on ebay Australia mate.