piano chord
D♭dim
D♭1F♭♭3A♭♭♭5
Two minor thirds stacked. The fifth is diminished, so it cannot be dropped without losing the chord.
Written the other way round it is C♯dim — the same twelve keys on a piano, a different piece of notation.
What is true of it
D♭dim is D♭, F♭ and A♭♭ — 1, b3 and b5 counted from D♭.
A♭♭ is a double flat, and it has to be: every letter from D♭ upwards is used once, so the b5 cannot be written any other way.