piano chord
A♯6
A♯1C𝄪3E♯5F𝄪6
A major triad with a sixth added. The same four notes as a minor seventh chord a third below.
Written the other way round it is B♭6 — the same twelve keys on a piano, a different piece of notation.
What is true of it
A♯6 is A♯, C𝄪, E♯ and F𝄪 — 1, 3, 5 and 6 counted from A♯.
C𝄪 and F𝄪 are double sharps, and they have to be: every letter from A♯ upwards is used once, so the 3 cannot be written any other way.
These are also the notes of Gm7/A♯. 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.