I have a feeling that this is the overwhelming answer you are going to get : No such thing as average, for any date-or-type coin. I've gotten seateds, gold coins, reales, etc.... that were only an inch deep. And I've gotten zinc pennies that were a foot deep . Doh !
About the only place where coin depth is stratified, is in manicured turf. But even that will vary from park to park, in every single location. I know parks where the wheaties and silver tend to start at 3 or 4". And I know other parks where I won't even dig them unless they are 8" or more (lest they're likely to be clad).
And on the beach after storm erosion, there is utterly no rhyme or reason to depth vs age. And in dry terrains (chaparral, desert, cow pasture type stuff), seems like there's no rhyme or reason.
If you're objective is to get old coins, then the "trick" is not always depth. The "trick" is: Location location location. Yes it's good to have high-end power-house machines. But the much bigger part of the formula is: Where you hunt.
I just Started Detecting with a tracker iv and i was WONDERING what is the average depth of:
