/usr/lib/ocaml/apron/box.cmxa is in libapron-ocaml-dev 0.9.10-9+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ocaml/apron/boxMPQ.cmxa
/usr/lib/ocaml/apron/boxMPQ.cmxa