One of the examples of how uncertain our knowledge about the history of women's nuns in Poland is still, is the matter of the religious affiliation of a monastery founded in Bydgoszcz in 1615, and dissolved only in the 19th century by the Prussians. This monastery undoubtedly belonged to the Franciscan family, but the problem is whether it was the so-called The Second Order, i.e. the Poor Clares, living according to the rule of St. Clare, or the Third Order in its community form, Tertiary sisters living together and at the beginning of the 15th century, by the decision of the Council of Trent, they were cloistered in our country, and living according to the so-called The Rule of Penitents or the Third Rule of St. Franciszek. Research on the record book of the Bydgoszcz monastery allowed us to establish its monastic identity: it was not a monastery of the Third Order but of the Second Order, not the Rule of the Penitents, but the Rule of St. Clara.