Sound like the silver insert is loose which is fairly common. Due to the way the two dissimilar metals are put together and the difference in the metals when they are subject to heat or cold it is not uncommon that the silver insert becomes loose and can rotate out of position. Not classified as an error. Now if the back of the brass rim were correctly oriented it would indicate a loose die in manufacting and would be an error. Just being rotated does not change the value of the strike.