piano chord
G♭m6
G♭1B♭♭♭3D♭5E♭6
A minor triad with a major sixth added, which is why it is not simply a minor chord with a flat seventh.
Written the other way round it is F♯m6 — the same twelve keys on a piano, a different piece of notation.
What is true of it
G♭m6 is G♭, B♭♭, D♭ and E♭ — 1, b3, 5 and 6 counted from G♭.
B♭♭ is a double flat, and it has to be: every letter from G♭ upwards is used once, so the b3 cannot be written any other way.
These are also the notes of E♭m7♭5/G♭ and D♯m7♭5/G♭. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
On an instrument that cannot reach all 4, the 5 goes first, in that order.