piano chord
Fm6
F1A♭♭3C5D6
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
Fm6 is F, A♭, C and D — 1, b3, 5 and 6 counted from F.
These are also the notes of Dm7♭5/F. 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.