I always wanted to do my own test on the US 1$ gold coin.This one is dated 1852 with a small hole drilled. The charts I've seen have always claimed 129(-132) for a US One Dollar Gold Coin.My results for a 1852 $1 US gold coin on top of the ground and sweeping with a 800 tornado coil.The sweet spot 1-4 inches away from coil will give a steady ID tone 137-138 further distance 4-6 will give a ID bounce of 140s steady 142-147.At the very end distance of detecting for this very small coin 6-9 inches the reading climbs to higher numbers 150-160.My hypothesis in the field if you have a reading anywhere in the 140s and with the coil closer to the ground the ID numbers lower to around 138 this may indicate a US gold dollar.I tried an air test with the 10 inch tornado coil and had the same results,I did notice all most like a null effect at the outer range and will give a bounce in the low 160s to 140s.The US dollar gold coin is very small(smaller than a 1/2 dime). There may be a lot of these lost over the years waiting to be found. Thanks Ron