Then there are the other people who believe that coins of different sizes sink at a slower rate than others because of their physical size (not the weight of the coin), There is a forum in the U.K. that swears by this and they also sell a machine that does not go much deeper than that! I don't know if I can mention the machine or not, so I'll just give the initials....C.S. My friend is testing this theory. Out back on his property he laid a silver dollar, a silver half, a nickel, a penny, and a dime on top of the ground, and 4 years later they are only about 1/2 inch deep. Only covered by decaying leaves. His soil is sand on top and clay about 18 inches deep. The physical diameter smaller coins will often be found deeper than most halves and dollars in my area, only because the parks I hunt are flood plain parks! The inside curve of the land coins will be really deep ( when the water goes down, the river deposits a sand bar over any lost coins) On the other side of the river, the fast moving water (SCRUBS) the grass and removes soil, still leaving the grass. And I can find coins from the 1800's there only 4 or 5 inches deep! Go figure. Kids stepping on coins and other lost items, a drunk leaning against a nice shade tree (slash type pockets), kids rolling down hills, reel type lawn mowers cutting the grass (and coins), earthworms tunneling under, ground hogs tunneling under the ground all MAKE coins and stuff go deeper. Except when ground hogs dig their holes, check their dirt piles, quite often they dig coins for you and deposit them in their piles! These are just some of the variables in "why was that coin only 4 inches deep" It should've been deeper for that age! I personally have dug I.H.'s at only 2 inches deep on the outside curve in a park, and 1973 pennies at 13 inches on the inside curve of the same park, when this little creek goes over its banks, the water in the park gets 10 feet deep in a hurry. And I have gone to the park after the water retreats, only to see new sandbars on the inside curve of the park where the water has gone down...........NGE