What the sources claim for it
Identity, mechanically derived. The character is a compressed spelling of the name under a planetary authority.
History
Where does Characters Derived from Names come from?
Agrippa's third book sets out a method for making a character for any spirit whose name is known. The name is written in Hebrew letters, the letters are converted to numbers, and the numbers are plotted on the magic square of the relevant planet; the path connecting them, marked at start and end, is the character. Nothing is invented — the sigil is a function of the name and the planet.
That makes these the opposite case to the Goetic seals, which cannot be derived from anything. The distinction is worth keeping. One tradition holds that a spirit's mark is generated by its name; the other holds that a spirit's mark is simply known. They produce completely different-looking books.
Afterwards
What did it turn into?
Revived by the Golden Dawn as the rose-cross method, and now the standard technique in modern sigil practice — where the letters plotted are the operator's stated desire rather than a spirit's name.
Which texts describe it?
Oldest first, with what each one does with the mark. A mark described in a Bronze Age incantation and a mark first drawn in a seventeenth-century manuscript are different kinds of claim, whatever the shape has in common.
Renaissance & Early-Modern Occult Angelology
Agrippa, Barrett, and their compilers · 16th-19th c. · Latin and English
Agrippa gives the derivation rule and the planetary squares it runs on.
Read Renaissance & Early-Modern Occult Angelology in full ↗Cover: Public domain · Otto Rietmann · Wikimedia file page
The Magus, or Celestial Intelligencer
Francis Barrett · 1801 · English
Barrett reprints the method with English examples.
Read The Magus, or Celestial Intelligencer in full ↗Cover: Public domain · Unknown author · Wikimedia file page
Nearby
Related marks
The Tetragrammaton
Four letters that stopped being pronounced and became, in consequence, the most powerful thing you could write on a piece of equipment.
The Seal of Solomon
A signet ring, not a shape. The Testament of Solomon makes it the instrument by which every demon in the book is compelled to give its name.
The Brass Vessel
The container the legend says Solomon sealed the spirits into, thrown into a lake and opened by Babylonians who expected treasure. It is where the Ars Goetia says its seventy-two came from.
The Seventy-Two-Letter Name
Seventy-two three-letter names extracted from three verses of Exodus — and the reason the number seventy-two keeps appearing on both sides of this corpus.
AGLA
An acronym, not a word: Atah Gibor Le-olam Adonai, 'Thou art mighty forever, Lord', compressed to four letters and written on almost everything.
The Hexagram
Two interlocked triangles that were ornament almost everywhere before they were a Jewish emblem anywhere — and a spirit-binding seal in between.