The Golden Dawn's grade notation itself, pairing a grade number with a corresponding sphere on the Tree of Life, is publicly documented in Israel Regardie's published editions of the order's papers, material Regardie released decades after the order's own internal schisms had already fractured it into several successor bodies. Zelator is a grade whose published teaching, per general accounts of the order's curriculum, concerns elemental symbolism at an introductory level.
Regardie's published material, and the scholarly and popular literature that followed it, made public a curriculum the original order had kept internal to its own membership, a shift in availability that general histories of the Golden Dawn treat as a defining fact about how the order is studied today: almost everything now written about its First Order grades, this one included, rests on material that only became public well after the order's founding generation had passed.
As with every initiatory grade in this atlas, what is described here is the grade's documented structural and symbolic association as published in Regardie's editions and the scholarship built on them, not any reconstruction of ceremonial wording or recognition content.