Can't find name of this type of error on a coin 1 1

[OceanSpray669]

I have looked through all the official names of errors for coins. And I cannot find the name of this type of error. I have an 1838 seated liberty coin where the reverse is stamped at a 90° offset of how the coin is supposed to be it is centered properly however it's just 90° offset I would imagine that this is a very rare error as I cannot find the name can anyone help me with this and given the date of the coin that I have I would assume it is very valuable.

[EagleRJO]

It sounds like you are describing a rotated die error.  You can use the attached gauge to get a better measurement of that, but at that rotation it's not that rare and would only add some value.

https://www.error-ref.com/rotated_die_error/

[Sandon]

   Welcome to the NGC chat board.   

   Coins struck from rotated dies are relatively common on nineteenth century U.S. coins and not particularly scarce on more modern issues. Only pieces struck in a full 180 degree "medallic alignment", in which each side faces upright when turned on the same axis from side to side, tend to command significant premiums.