Silver coin issued during King Prithvi Bir Bikram Shah Dev dated 1830 B.S (1773 A.D). I have some similar coins released during King Prithvi Bikram Shah Dev but all the date in those coins are not correct time with the information we get from the history (https://en.wikipedia.org/wiki/Prithvi_Bir_Bikram_Shah).

Can anyone please explain about this?