Vъ… červьči in the colophon of the Pskov apostle of 1307: what does it mean?

The paper deals with the lexeme that has been thus far registered by the dictionaries of Old Russian merely in the colophon of the Pskov Apostle of 1307 (where it occurs in the locative form: červьci) and has been presumably interpreted as a variation of the Slavic name of a summer month (čьrvenъ / *čьrvьnь). Another text where the word comes up (a brief chronicle found in a miscellany dating back to the last quarter of the 15th century) allows to interpret it unambiguously as ‘cell’ (of a hand-shaped table for calendar calculations). However, the initial form (*čer(e)vьcь or *č(e)revьce) and the etymology of the word remain debatable.