hi jb! i'm glad to see your post. as always, i enjoyed reading it. i know that i stated it took me an hour and a half to two hours average to sweep an entire acre. i know that it sounds pretty optimistic. but, yes, on average, a couple of hours an acre. like most older hunters, i try to catch the feel of a spot and run off of that. i reckon it's a sixth sense i'm still trying to develop. fields out in the country around my area either yield a lot or very little. there doesn't seem to be an in between, it's like feast and famine.
lots of old iron and sometimes a nice coin or two will pop out, or the occasional civil war bullet or two. if old iron relics were in demand, i'd be a gazillionaire. there's been lots of times where i was diggin' so many relics and coins [good and bad] on a small plot of ground that i really thought i would never finish it! and it's really amazing how after a good rain or the farmer turns his dirt how new an old spot can be. sometimes, it's as though i was never there! targets and beeps everywhere! changing machines like you did on an old hunting ground gives good results, too. that's a lot of the reason i recommend to many people to own and use at least two machines. what one machine misses, the other will pick up.
you sure have found a lot of coins in that one spot! it sounds good, so it must be good. congratulations on all your finds, good luck and hh,