Here's how you would "reasonably" know:
If a site in question dates, let's say, to 1900. And if ...... after 100 coins dug there, it becomes obvious that coins lost at those earliest of usage years, are at no deeper than 6", ...... well .......... think hard. Sure, an 1880s loss might be deeper. But wait! : If the origination of this park or school or whatever was/is 1900 (and not earlier), ....... then .... think hard.
For beaches (where sand gets re-arranged), or furroughed fields (where plows can put them all over the depth landscape) , or any other disturbed surfaces, sure: this goes out the window. I'm only talking about places where 100's of test-sample-age targets begin to show a correlation. Then a "reasonable" person begins to deduce that ....... there's a stopping point in depth.
Also, some grounds actually have a bedrock, to which nothing can sink deeper. Think hard, what happens to depth in such places?
If a site in question dates, let's say, to 1900. And if ...... after 100 coins dug there, it becomes obvious that coins lost at those earliest of usage years, are at no deeper than 6", ...... well .......... think hard. Sure, an 1880s loss might be deeper. But wait! : If the origination of this park or school or whatever was/is 1900 (and not earlier), ....... then .... think hard.
For beaches (where sand gets re-arranged), or furroughed fields (where plows can put them all over the depth landscape) , or any other disturbed surfaces, sure: this goes out the window. I'm only talking about places where 100's of test-sample-age targets begin to show a correlation. Then a "reasonable" person begins to deduce that ....... there's a stopping point in depth.
Also, some grounds actually have a bedrock, to which nothing can sink deeper. Think hard, what happens to depth in such places?