V3i with standard coil; Have permission to dig around an abandoned older housing camp used for many years by immigrant workers during MI planting/picking seasons. This place is like digging in a tab top/beer cap collection point.. I am finding many new pennies and dimes but having a rough time getting thru to any deeper stuff. Don't know what the signatures will be but it would seem reasonable that I would find some older Mexican coins and hopefully jewelry. The nice thing is that I do not have to worry about how I dig or how I fill the holes as the landowners are going to be knocking down the building and plowing the ground for planting in the future. What would be a good coil for the V3i in these conditions?