[4] The cup is also a very rare example of a complete Roman cage-cup, or diatretum, where the glass has been painstakingly cut and ground back to leave only a decorative "cage" at the original surface-level.

Most cage-cups have a cage with a geometric abstract design, but here there is a composition with figures,[5] showing the mythical King Lycurgus, who (depending on the version) tried to kill Ambrosia, a follower of the god Dionysus (Bacchus to the Romans).

The process used remains unclear, and it is likely that it was not well understood or controlled by the makers, and was probably discovered by accidental "contamination" with minutely ground gold and silver dust.

[7] It is estimated that to a conventionally composed Roman glass flux 330 parts per million of silver and 40 of gold were added: "These particles were precipitated as colloids and form a silver-gold alloy.

[15] Like the British Museum's other spectacular work in Roman glass, the cameo glass Portland Vase, the cup represents to some extent the extension of skills developed by cutters of engraved gems, or the larger hardstone carving of vessels in semi-precious stones, which were luxury arts with enormous prestige in ancient Rome.

No carved gemstone vessels directly comparable to either work are known, but the general taste behind these extreme exhibitions of glass-making skill is one formed by objects in natural stones like the Coupe des Ptolémées or the Rubens Vase.

[18] There are various small losses, of which the face of the panther is the most significant, and the cup is cracked; the British Museum has never removed the metal rim for this reason.

[22][23] This effect, like in the original Lycurgus cup is due to small amounts of silver and gold nanoparticles, of the proper size and shapes, embedded in the 3D printable material.

The figure of Lycurgus, bound by the vine and naked apart from boots,[24] is flanked on the left by a crouching Ambrosia, at a considerably smaller scale.

Behind her one of Dionysus's satyrs (shown with a normal human form) stands on one foot as he prepares to hurl a large rock at Lycurgus.

[25] To the right of Lycurgus comes first a figure of Pan,[26] then at his feet a rather canine-looking panther, the traditional companion of Dionysus, whose face is missing but was presumably snapping at the king, and then the god himself, taunting him with his right arm extended in an angry gesture.

Dionysus carries a thyrsus, the special staff of the god and his followers, and his dress has an Eastern, perhaps Indian, flavour, reflecting what the Ancient Greeks generally believed (perhaps wrongly) about the origins of his cult.

[27] It has been suggested that this not very common scene was a reference to the defeat in 324 by the Emperor Constantine I of his co-emperor Licinius, who was killed in 325 after a period under close guard.

The closest parallel to the scene on the cup is one of the apse mosaics in the triconch triclinium at the Villa del Casale, Piazza Armerina, which may also refer to Licinius.

The foot continues the theme of the cup with open-work vine leaves, and the rim has leaf forms that lengthen and shorten to match the scenes in glass.

100 Years of the National Art Collections Fund", and in 1987 in "Glass of the Caesars" in the British Museum, Cologne, Milan, and Rome.