My best so far was a VF 1906 M half sovereign for a tad over spot <$175. I also managed to snare a VF 1893 M 12 pearl half sovereign from a second hand shop for spot. Both have been graded by an ANDA valuer so they are the real deal.
I'd have to say the 1856 half sov I picked up last weekend for 400. (Crap) pictures in the gold coins thread. Looking at other examples currently for sale I reckon it's worth probably 2-3 times what I paid for it. Today. In 10 -15 years time though .......