piano chord
Bm6
B1D♭3F♯5G♯6
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
Bm6 is B, D, F♯ and G♯ — 1, b3, 5 and 6 counted from B.
These are also the notes of G♯m7♭5/B and A♭m7♭5/B. 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.