Draft in Bellarmine's own hand: Roma, ARSI, Opp. N.N. 241, fol. 132r.
The verso side contains a few lines (not in B's hand: 'Il S. Card.le Bellarmino non s'intromette nel fare Priori ne altri officiali della religione de Celestini ...') that do not help point the date of the letter. Its position in the manuscript cannot help here either. (The little organisation there is, is by correspondent.)
Given the point of the collection where Tromp places this letter, one could assume that he would have dated it about 1601-1602. Yet, nothing in the text points to this assumption, so the date field has been set to 'unknown'. The same applies to the name of the recipient, as it cannot be identified without a date. The "vicar" can only be the vicar of the bishop of Gaeta.