It all depends on your location , the type of soil , and how deep the top soil is there. Generally , a coin will only sink until the density of the soil causes it to stop and in most locations that is around 10 inches or less , unless of course it is helped along by other factors causing buildup of soil on top of it. Ive detected a lot of different sites in 4 different states , over the course of atleast 25 years , and at almost every place even the old coins were less than 10 inches deep , usually mixed with the more modern coins. Ive only noticed 2 exceptions , when the organic matter topsoil was more than a foot deep or the ground was saturated with water for most of the year I have found a couple coins a little deeper but thats not the case in most places. Many people fear their detector is not going deep enough and thats why they cant find the good coins when in reality the coins just may not be there to find. There is a reason most detectors are designed to penetrate the ground at around the same depth give or take , its kinda like cars being designed to operate most efficiently at about 55 mph. , thats about the average of what you can expect to find targets at in most places , or in the case of the car example thats gonna be your average speed limit in most places. Specialty coils are available to "help" you get better depth in a few places that dont fit the "normal" depth range for one reason or another depending on the situation but they arent necessarily gonna help you find more or deeper coins in most places since they "usually" stop sinking well within range of your stock coil.