here). Sometimes the record of a provenance is written, and can get lost (see here), or sometimes collectors mark items in the collection. When there is an inventory number on an antiquity it can be hard to tell where that number came from.
It's unusual to see a Roman sculpture with a seal of a Renaissance collector, but they do sometimes come onto the art market. The seal on this head at Galerie Chenel proves that it was once in the Venice collection of Giovanni VI Grimani, who was Patriarch of Acquilea (1545-1550 and 1585 to his death in 1593). The Grimani collection was one of the best collections of antiquities in the Renaissance (JSTOR), and some of it was brought to Paris by Napoleon. Some pieces ended up in the Louvre, this one in a French private collection.
What's interesting is the Grimani's collection is quite well documented, since he gave some of his sculptures to the Republic of Venice in 1586 (JSTOR) - and in 1594-6 the Republic had leads seals attached to the sculptures to commemorate his gifts. But this Antonine head is neither in the 18th century catalogue of the collection nor in the accompanying drawings of it according to Chenel ... But I do wonder if this engraving after Zanetti in 1740 on a Renaissance bust might not be the Chenel head:
below), as usually identified ... although frankly it could be either one in the engraving: