piano chord
Bm7♭5
B1D♭3F♭5A♭7
A diminished triad with a minor seventh rather than a diminished one — half diminished, and not the same chord as dim7.
What is true of it
Bm7♭5 is B, D, F and A — 1, b3, b5 and b7 counted from B.
These are also the notes of Dm6/B. Which name is right depends on what is underneath and what came before — the notes alone do not decide.