The picture’s style suggests a date of about 1618–20, when van Dyck collaborated with Rubens. The paper support appears to be from an account book written in Italian with traces of Flemish (possibly proper names). Perhaps the paper was used previously by Rubens, who often wrote in Italian, but it is far from certain that the barely discernible writing is in his hand. (https://medium.com/@wendymac/what-does-the-mets-new-online-collection-mean-for-art-students-5d957b09aaf8)