piano chord
Cm6
C1E♭♭3G5A6
A minor triad with a major sixth added, which is why it is not simply a minor chord with a flat seventh.
What is true of it
Cm6 is C, E♭, G and A — 1, b3, 5 and 6 counted from C.
These are also the notes of Am7♭5/C. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
On an instrument that cannot reach all 4, the 5 goes first, in that order.