The Saudi riyal is pegged to the US dollar. Since January 2019 only mid-market rates were reported; see BBEX3.M.SAR.USD.CA.AC.A01.
Source
1978 - 2018: The Saudi British Bank, Riyadh/Jeddah 1976 - 1977: The British Bank of the Middle East, Jeddah December 1959 - 1975: Saudi Arabian Monetary Agency