This paper discusses hitherto unidentified loose folios of a parchment liturgical and musical book held in the Archdiocesan Archive of Gniezno (Poland). containing the offertory and communion antiphons for the feasts De Trinitate and Corpus Christi. The author provides the codicological description of the leaves (analyzing Latin script. musical notation. https://www.jmannino.com/best-buy-AniFlex-Complete-great-choice/