Quarter is for size comparison. I believe this is made of lead and has 3 dots. I have no idea where to look for something like this. It weights 69.8 grams.
It's not a "coin" - the ancients didn't make square lead coins.
If it is ancient, it might be a weight.
Do you have any provenance (where it was found)? If so, then perhaps we could try to find out if it weighs 3 times the local weight unit.
It was given many years ago to me. I don't know anything else other than I was told it was possibly an ancient coin....unless I was confused and it is a weight.