here: oh, and it was published in the 1930s, so it's not looted. Whilst it's nice to see that whoever wrote the catalogue found the publication, I'm rather surprised to see they are listing it as 4th century AD ... 'coz anyone with eyes can see it's an early to mid Hellenistic attempt at depicting Alexander the Great, almost certainly made in Egypt where porphyry came from and where the only people that could carve it where to be found.
My pet peeves are people trying to assign big "names" to heads (I showed photos of the only certain Greek-style statue of Cleopatra VII recently, and the statue is identified by inscription but headless); and people trying to assign anything in porphyry to the fourth century AD ... there were relatively few late Roman examples, and most of those re-carved earlier images. And all the late porphyry portraits are of emperors, which this clearly is not. Doh!