Золотая книга сказок / Божена Немцова ; перевод с чешского А. Серобабина. (OCLC #959887720)
Whenever I create records in OCLC with non-Roman characters, I notice that it helpfully adds an 066 field to my record, like:
066 __ǂc (N
In this case, the code “(N” indicates the presence of Basic Cyrillic script in the record, mostly as a signal to the user that extra processing may be required.
So why the weird code? I’d wondered this for a while, and finally looked it up. Longer blog post coming soon.