You may be right Scubadetector.
I'm not a coin hunter so I don't have that many old coins.
You have lots more than me. 25 years ago I had a lot when
I was coin shooting back then. I sold or lost those.
But, most of the old coins I have found came from the most
hunted park in Arkansas. Fair Park.
Only a few were deep. That I can remember. But, I have found
artifacts that were really deep.
I've found a bunch of jewelry in the big tot lot there.
Most of the ground is hard there. I don't think they can sink.
But some get covered up.
I found an early 1900's quarter sitting on top of the ground there.
I hunted a WW I training camp. Found lots of artifacts. They
were all deep.The only coin I found was in soft ground. It was
a 1920 penny about 2 or 3 inches deep.
Don't have much to go on, but you can see why I said what I did.
Never really tried to go real deep. Sometimes I couldn't get 3"
with the older MD's I had, and the bad ground conditions, that, I
did not understand.
HH,