There is confirmation via reader e-mail and personal observation that license plates have entered the O’s. This did not happen with the 1997 series, which skipped from N to P.
It did, however, happen with the 1986 series, which began to be issued in January 1985. On Nov. 17, 1984, the Cedar Rapids Gazette had a front-page story with a photo of plates the Linn County Treasurer’s Office had already received. First up was OQA 000. This series was exclusively the second half of the alphabet, and the fact that Linn got O’s indicates that the largest population counties may have gotten them out of order before an alphabetical-by-county issuance.
I don’t think that many Linn County residents are members of the Order of the British Empire, though.