Jan Walter of Chojnice (*about 1445, †1512), initially a vicar, and then a parson of St. Peter and Paul’s Church, as well as a secretary of Gdansk City Council, is one of the best known figures associated with the old book culture in Gdansk. The article describes one of the aspects of his bibliophilia: book covers marked with supralibros. It first discusses works by local bookbinders made for Walter, and then analyses a supralibros in the form of a miniature oval featuring the mark of a bibliophile (the head of a Negro) against the background of the European and local tradition of marking books in late Middle Ages. As a result, it is demonstrated that six from among the Gdansk citizen’s books we currently know, which contain the mark, were provided with it secondarily. This is mainly indicated by the non-typical locations of the supralibros – each one is in a way “squeezed in” between the regularly spaced elements of the blind embossing adornment of the covers.