As well as the fragments of the original I Modi, there is hidden away in the British Museum's infamous "Cupboard 205" another erotic portfolio that has strong links to the original. This edition is a series of erotic drawings by Count de Waldeck.
Waldeck made the reproduction of I Modi some time around the mid 1850s even though by then all copies of the original should have been destroyed. He claimed to have seen an original set of I Modi prints in a convent near Palenque in Mexico as well as tracings by French sculptor Francois Antoine Gerard. His story is dubious since there is no such convent and he was known for occasionally exaggerating his stories. He may have at the very least seen the fragments now in the British Museum since the fragments can be easily matched to his drawings. Also, many of the postures shown in the 1550 woodblock edition (which was only rediscovered in the early 20th century) are almost identical to Waldeck's. Too identical to be a coincidence.
It is unlikely he had access to a woodblock copy. Although they are very similar, there are notable differences between them. There is also no way he could have made such similar drawings from just the I Modi fragments.
There are interesting differences between this set of drawings and the woodblock copy of I Modi. Firstly, Count de Waldeck erroneously believed there were 20 prints in the original I Modi and so made 20 drawings. This is more than likely because Renaissance historian Vasari reported there were 20 prints even though we know from letters written by Aretino that there were definitely only 16 prints in the original. Another difference is that none of Waldeck's drawings match Posture 3 of the woodblock edition. These differences lead me to believe he never saw an original I Modi, though he may have seen some kind of copy that we don't know about today.
I have labeled the drawings so that they match up with the surviving woodblock edition of I Modi, though there are no equivalents for the ones labeled between 17 - 21.