Silver coin issued during King Prithvi Bir Bikram Shah Dev dated 1830 B.S (1773 A.D). Little bit confusion on issued date on this coin. According to the history information King Prithvi Bir Bikram was born in 18 August 1875 – 11 December 1911 but the date printed on the coin is before the King was born (

Can anyone please explain about this?