Sorry for the late response, as I see you already ordered your X-TERRA. But rest assured you bought a fine detector. One thing I would recommend, however, is to see how the stock coil performs before spending a lot on accessory coils. The reason I say that is because the X-TERRA is unique in that it offers coils in concentric and DD. And some come in one of three different frequencies. I know you said you planned to coin/relic hunt, with an occasional trip to the beach. Knowing the ground phase readings for the stock coil will help determine what might work best for you, at the sites you hunt. Lower frequencies are best suited for higher conductive targets such as silver and copper. Higher frequencies are best suited for lower conductive targets such as gold. Lower frequencies will detect larger targets at greater depths than higher frequency coils. And higher frequency coils are better at detecting smaller targets than lower frequency coils. DD coils are designed to better neutralize the effects of heavy mineralization. If you hunt areas with heavy mineralization, then the DD coils will provide better depth, greater sensitivity and will be more stable. If your soil is not heavily mineralized, then the concentric coils will obtain more depth and give more accurate TID. On the 705, the "break point" for whether I want to use a DD or a concentric is the ground balance number of 28. If I am able to properly GB my 705 and achieve a ground phase number that is greater than 28, I know that a concentric will be my best choice. If when I properly GB my 705 and achieve a ground phase number that is less than 28, I know that the mineralization is high enough that a DD coil will work best. I hunt for old coins at old sites. If I am hunting an area where I need superior target separation, regardless of my GB number, I chose the small 6-inch DD at 18.75 kHz. If I am hunting a wide open area, my preference is the 9-inch concentric at 3 kHz. There is not a better "silver coin killer" combination for the types of places I hunt. JMHO HH Randy