Changing the bequeathed currency from silver riyal to paper riyal

Q: I am Zayd ibn Rashid ibn Khurayf. My father Rashid died 26 years ago. Before his death, he had bequeathed that I buy a 60-riyal Ud-hiyah (sacrificial animal offered by non-pilgrims) on an annual basis, and that such a sum of money be taken out of his real-estate located in Al-Hulwah in the district of Al-Gharis. The currency of that time was the Arabic silver riyal. My question is: Shall I take on an annual basis sixty banknote riyals, sixty silver riyals or their value in currently used banknotes out of such real-estate to buy an Ud-hiyah therewith?

(Part No. 16; Page No. 358) A: If the reality is as you mentioned, you shall take out of the real-estate the value of sixty silver riyals in current banknote Saudi riyals on an annual basis to buy an Ud-hiyah therewith. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.