The bottom of the vase was a cameo glass disc, also in blue and white, showing a head, presumed to be of Paris or Priam based on the Phrygian cap it wears.

It may have been added in antiquity or later, or is the result of a conversion from an original amphora form (paralleled by a similar blue-glass cameo vessel from Pompeii).

Interpretations of the portrayals have included that of a marine setting (due to the presence of a ketos or sea-snake), and of a marriage theme/context, as the vase may have been a wedding gift.

It is based on the skill of the famous Greek carver of engraved gems Dioskourides, who is recorded as active and at his peak circa 40–15 BC and three of whose attributed cameos bear a close resemblance in line and quality to the Portland vase figures.

This theory proposes that the first two figures are Gaius Octavius, father of the future emperor, and Atia, his mother (hence Cupid with the arrow) who had a dream of being impregnated by Apollo in the form of a sea serpent (ketos), note the snake's prominent teeth.

The onlooker with his staff, could be Aeneas, a hero of the Trojan Wars who saved his father by carrying him over his back (hence his hunched position, and his Trojan beard) and who is believed to have founded Rome, and from whom the Julian gens, including Julius Caesar and Attia, claimed descent, witnessing the conception of Rome's future savior as an Empire, and the greatest of all the Emperors.

[citation needed] This vase suggests Octavian was descended partly from Apollo (thus partly divine, shades of Achilles), whom he worshiped as a god, gave private parties in his honor together with Minerva, Roman Goddess of War, from the founder of Rome, and his connection to his uncle Julius Caesar, for whom as a young man he gave a remarkable funeral oratory, and who adopted him on his father's death, when he was only four.

[citation needed] Cameo glass vessels were probably all made within about two generations,[9] as experiments when the blowing technique (discovered in about 50 BC) was still in its infancy.

[11] Jerome Eisenberg has argued in Minerva that the vase was produced in the 16th century AD and not in antiquity, because the iconography is incoherent,[13] but this theory has not been widely accepted.

[14] One story suggests that it was discovered by Fabrizio Lazzaro in what was then thought to be the sarcophagus of the Emperor Alexander Severus (died 235) and his mother, at Monte del Grano near Rome, and excavated some time around 1582.

[5] The first historical reference to the vase is in a letter of 1601 from the French scholar Nicolas Claude Fabri de Peiresc to the painter Peter Paul Rubens, where it is recorded as in the collection of Cardinal Francesco Maria Del Monte in Italy.

[5] Between 1778 and 1780, Sir William Hamilton, British ambassador in Naples, bought the vase from James Byres, a Scottish art dealer, who had acquired it after it was sold by Cornelia Barberini-Colonna, Princess of Palestrina.

[16] The 3rd duke lent the vase to Josiah Wedgwood, who had already had it described to him by the sculptor John Flaxman as "the finest production of Art that has been brought to England and seems to be the very apex of perfection to which you are endeavoring".

One of them is on display in the Wedgwood rooms of the Lady Lever Art Gallery in Port Sunlight The vase also inspired a 19th-century competition to duplicate its cameo-work in glass, with Benjamin Richardson offering a £1,000 prize to anyone who could achieve that feat.

Taking three years, glass maker Philip Pargeter made a copy and John Northwood engraved it, to win the prize.

The owner of the vase declined to bring a civil action against William Mulcahy because he did not want his family to suffer for "an act of folly or madness which they could not control".

[32] He reportedly used "new adhesives" for this restoration, which some thought might be epoxy resins or shellac, but were later discovered to simply be the same type of animal glue that Doubleday used in 1845.

Although the vase was shown at the British Museum as part of the Glass of the Caesars exhibition (November 1987 – March 1988), it was too fragile to travel to other locations afterwards.

Conservation scientists at the museum tested many adhesives for long-term stability, choosing an epoxy resin with excellent ageing properties.

[34][35] Little sign of the original damage is visible, and, except for light cleaning, it is hoped that the vase should not require major conservation work for at least another century.