I haven't taken mine out yet. I just bought it and put it together. Tested a few objects in the house, here are the values I get:
Kennedy half (clad) ........ 93
Newer quarter ............... 88
Newer dime .................. 83
Wheat penny ................ 82
Zinc penny ................... 77
Newer nickel ................. 58
I did not have any silver coins readily available to test
Ring ........................ 80-88
10k gold class ring .... 59-72, 75
Steel pinky ring ........ 53-54
The first ring above is a class ring type ring, but it is not gold. I also do not think it is silver. I am not sure of the metal they use. Both rings gave different values depending on how they were sitting. The highest value is if the ring is laying flat. When I laid it on its face or placed it in a different orientation, the values moved around and often did not give the same value on consecutive sweeps.
I then tested some junk - a couple old keys, a small uneven ball of foil about the size of a half dollar, and a newer style pop-top.
Keys .................... 78-82
Small ball of foil .... 60-66 (very erratic, values jump around alot)
Pop-top ................ 58
I also tested a paper clip - it did not even register on the detector with the coil right on top of it.
These are first time 'air tests', just done on the floor of my house. No interference or anything was apparent. I would be interested to know if these are the same values others see with the Delta 4000 for similar objects in the ground.