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 A♭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♯.