piano scale
G♭ Dorian
G♭1A♭2B♭♭♭3C♭4D♭5E♭6F♭♭7
Minor with a natural sixth. The second mode of the major scale.
The same sounds spelled from the other side are F♯ Dorian.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
G♭WA♭HB♭♭WC♭WD♭WE♭HF♭WG♭
What is true of it
G♭ Dorian is G♭, A♭, B♭♭, C♭, D♭, E♭ and F♭, and back to G♭.
Its steps are W – H – W – W – W – H – W, where W is a whole step and H a half.
Written correctly it needs 8 alterations, B♭♭ among them. That is what the letters force, and it is also why nobody writes music in this key: the same notes spelled from the other side are easier to read.
On the same tonic, G♭ natural minor differs from it by exactly one note.
Chords made only of these notes
D♭mminorD♭m7minor seventhE♭dimdiminishedE♭m7♭5half-diminished seventhG♭mminorG♭m7minor seventhA♭mminorA♭m7minor seventh
Found by testing every chord in the catalogue against these 7 sounds, not chosen.