Just wondering if anyone has an opinion on which coil in general will provide the best detection depth for silver. I am using the standard double d coil but am intrigued by the larger butterfly coils as well as the 13" double d coil. I have a site that has very little trash and lots of deep silver coins, which I believe I have hunted out using the standard coil. But I have to believe there are some deeper silver coins that I haven't been able to reach. I've played around with the sensitivity, moving from auto to as high as 18 and had some luck in getting deeper coins, but am now ready to try some other coils if people think that will make a difference.