Zakaat not paid on wedding jewellery

Respected Mufti, I have recently established that my elderly mother has not paid Zakaat on her wedding Jewellery. My father passed away in 1981 so I am unable to establish if Zakaat was paid by him on my mothers behalf. She is unsure. this year I had the jewelery valued and Zakaat has to be paid on it. Please advise as to how I should go about calculating past Zakaat and what advice I should give my mother as this is of concern to me and my mother. My mother has been married for close on to 50 years.

Your valuable guidance would be most appreciated.

Was-salaam