This could have been clarified by probate, which I gather didn’t occur. Regardless, you possess the item, they claim it belonged to your mother, that it then should be theirs (I don’t know why). But, it is too old to open an estate, and you aren’t legally or ethically obligated to turn it over to them. You do not need to surrender it to them and they can not get a court order to make you do so.
