i recently got a teknetics delta 4000 and doing some tests with coins now everything reads good but on a nickle when i bury it at a few inches it reads as a quarter with a high tone and when i take it back out of the hole it reads as a nickle again theres no other metal in the hole i just tried it again and buried the nickle at like like 3 inches and it reads good but when i go to like 4 inches or more it reads at a quarter again Weird! any ideas thanks clad king