I have only pulled up a jar lid twice. Both times my heart really thumped as I too imagined coins being in a jar. In this area of SE KY suppposedly it was very common for peps to bury what little money they had often. I suppose the same is true of other parts of the country though. All the same it certainly has the heart racing when I pull them out.
A construction site I did where 2 old Barber Halfs came out came from such a coin spill. I found out much later after finding them that 40 years earlier that when they were tearing down the building that used to be there they had dozed one such jar. A while later the person who told me showed me a picture (polaroid so not the greatest) of a big pile of coins. The jar was busted by the dozer, but when they saw half of a jar full of coinage they looked around and came up with a nice collection of halfs, dollars, and other coins. I can only imagine that the 2 halfs found there were reminants of that jar that escaped them during that construction and 40 years later those 2 poped up.
After finding those 2 and hearing of that story I went a bit nuts digging at that area. There was a lot of items that were shaped exactly like can lids all over the grounds of this large construction area. I must have dug up 70 of them or more. Sadly no big coin find. Oh well LOL>
Sad thing is if I could detect right now I would keep diggin em up.
Rev