That's a nice score TM, lotsa silver and a few coppers 1958 being the key number in that lot for looking at a reason for them being there,...is the nuggetty looking find heavy enough to feel like the real thing ? if it's as heavy or heavier than a similar sized bit of lead(by looks) than you might be onto something,...or it could be a blob of brass blackened from a fire maybe ?,...curiouser and curiouser !