I was metal detecting today and I got a faint hit but it showed up as a quarter on the detector so I got all excited thinking it was going to be a old cion so i dug atleast 8+ inches down i pulled a MODERN PENNY!!! how do those get that deep!
Lots of explanations - Could be that the ground has been turned over or disturbed. Could be the coin fell into an existing hole when it was lost. Could be that the target was actually on the side of your hole and fell down to the bottom while you were digging (this happens a lot) Or it just could be soft, wormy deep topsoil where stuff ends up deep.
I find the same so I rationalize it like this.....I personally think the earth is aboil.
Targets are constantly churing. Factors like soil type, freeze and thaw, animals, plants, and insects...etc, can affect the rate of movement.
My test garden after a couple years has a few coins that have moved from their original location. I suffer moles in the yard.
Thats my theory.