piano chord
G♭dim7
G♭1B♭♭♭3D♭♭♭5F♭♭♭♭7
Three minor thirds stacked. The seventh is doubly diminished, which is why it is written with a double flat.
Written the other way round it is F♯dim7 — the same twelve keys on a piano, a different piece of notation.
What is true of it
G♭dim7 is G♭, B♭♭, D♭♭ and F♭♭ — 1, b3, b5 and bb7 counted from G♭.
B♭♭, D♭♭ and F♭♭ are double flats, and they have to be: every letter from G♭ upwards is used once, so the b3 cannot be written any other way.