Your start position was: “I need all the information I can get” but getting information from you has been like pulling teeth. There will be questions you can’t answer (the interpretation of the numerals/date for example, which surely we must regard as a critical part of any solution for what it is) but there have been a lot of simple questions which you have ignored or evaded and basic information which you have not volunteered.
Material of Construction?
It appears to be lead with copper wire inlay, neither of which are actually confirmed and you don’t want to have any tests conducted on it. Fair enough if you don’t want to risk damaging it, but in the UK you can buy a twin-pack of 3M “Lead Check” swabs for £7.75 and I’d be amazed if you can’t get them in the US. You only need to swab a little dust off the surface to test, with no harm to the piece itself.
Is it solid?
You say it’s not a box and doesn’t open in that way, but that doesn’t mean it’s solid. You haven’t confirmed that it doesn’t rattle although your comments infer that it doesn’t. Since it has ‘seams’ and may have been poured in two halves (or multiple pourings) as has been suggested, you have no way of knowing whether something was inserted during the casting process (a coin, key or whatever for example), or if it has a void. A density calculation (see below) might help and an X-ray (as previously suggested) might tell you nothing at all, but surely is worth a try to see if anything shows up.
Size?
You say it’s 100 x 60mm with a width between 22 -27mm. But is the 100mm measurement the actual height from centre of the base to the apex or measured on the diagonal from corner to corner? You were also asked how many pieces the same size would fit into a circle but didn’t answer. You could easily establish this by repeatedly tracing it onto a piece of paper.
Weight?
Despite being asked several times, the only answer you have given is that it’s “heavy for its size”. An exact weight (with confirmation of the nature of the exact dimensions as above) would enable a calculation on its density and potentially help determine its composition or construction. Why don’t you want to provide this information? It might also be relevant if the piece has been made to an exact weight in terms of number of ounces.
The other face?
You have consistently avoided showing it to us, despite numerous asks. Some are calling it the back and some calling it the bottom but – just to be clear – what is being asked for is a picture of flipside to the face that has the ‘copper’ decoration. If it’s completely blank to the extent that it’s of no relevance then why don’t you just say so? Or is there some other reason why you don’t want to show it to us? If so, please at least give some indication of why, even if you still won’t show us. Are there some additional marks or letters that you think might be a code or something like that? I’m sure we’d understand if you didn’t want to show it for that reason, but you could at least offer an explanation.
Surface?
It was suggested that you look using a loupe to see it there is any sign that it was once painted, but you ignored the suggestion, or at least didn’t answer the question.
Find environment?
You say your father ‘unearthed this in a wooded area’ but have told us nothing about the actual environment in which it was buried, nor how long ago he found it. Was it wrapped in anything or just bare in the soil? Presumably not dry soil if in a wooded area. What is the explanation for the lack of corrosion on the ‘copper’ versus the corrosion of the ‘lead’. Has someone polished up the ‘copper’?
You’re hoping someone can provide “photos of things that look similar”. I would think the chances of that are between slim and none. And Slim left town. Surely this is going to be a one-off hand-crafted piece with no similar examples from elsewhere. Unless you believe it’s a slice from a bigger round ‘pie’ and the other matching slices are kicking around somewhere. That doesn’t seem very probable and surely, if any of them had turned up, someone would have been asking about them.
EDIT: Just seen @crabstang44's reply, made while I was typing... so the above may no longer be relevant.