piano chord
C♯m7♭5
C♯1E♭3G♭5B♭7
A diminished triad with a minor seventh rather than a diminished one — half diminished, and not the same chord as dim7.
Written the other way round it is D♭m7♭5 — the same twelve keys on a piano, a different piece of notation.
What is true of it
C♯m7♭5 is C♯, E, G and B — 1, b3, b5 and b7 counted from C♯.
These are also the notes of Em6/C♯. Which name is right depends on what is underneath and what came before — the notes alone do not decide.