piano chord
A♯add9
A♯1C𝄪3E♯5B♯9
A major triad with a ninth added and no seventh — which is what tells it apart from a ninth chord.
Written the other way round it is B♭add9 — the same twelve keys on a piano, a different piece of notation.
What is true of it
A♯add9 is A♯, C𝄪, E♯ and B♯ — 1, 3, 5 and 9 counted from A♯.
C𝄪 is a double sharp, and it has to be: every letter from A♯ upwards is used once, so the 3 cannot be written any other way.
On an instrument that cannot reach all 4, the 5 goes first, in that order.