Jeff,that’s excellent record keeping! It’s also a VERY clear indicator that If you have spent about the same time hunting these last 4 years,these particular sites are NoT going to allow for high coin counts. What they DO allow is a larger chance of finding those older coppers and weird denom coins that traditionally don’t show up as often on public ground(parks,schools,etc.)
It all depends on what you want to find. If you are going for it all and feel as if these defunct sites are the way to do it,I won’t argue. But if you’re looking for more silver,IMHO it has to be where a lot of activity occurred,and people had it in their pocket. To ME,it’s about return on my time,I won’t usually go hunt somewhere that MIGHT have something. I will go somewhere that DOES have something,because the odds of it having nothing are zero.
On your chart,the difference of 6 silvers to me isn’t an indicator of machine error or operator error,rather...the places you’re hunting do NOT have enough of what you want. Even though you seem to have access to a lot of them,it’s going to take a ludicrous amount of time to sort through them all and harvest the stragglers. Hunting a site with perhaps less area and more activity within that area will up your silver coins. The large coppers are big targets,any of those in public places are likely gone for the great part.
If you’re looking for that “spectacular find” or a “cache” or you don’t mind digging horse shoes,you’re on the right track,IMO. But the biggest thing you can do to change that “9” number is to NOT hunt where you’re hunting. I truly believe that.