EDIT: How is LL distinctly B/X, as opposed to BECMI, in what it presents? I'm just curious.
LL goes to ca 20th level (some tables extend higher) but does not have the additional complexity of the Mentzer Companion and Masters sets. Even the magic item tables seem derived from the Cook-Marsh Expert set. There's none of the Mentzer stuff like additional options at Name level, and it has the Cook-Marsh multiple Fighter attacks rule, for instance.