It's an interesting question; maybe he remembers. If it was a Lisp-1 when originally implemented, it became a Lisp-2 within the first year or two, using different properties of atoms (symbols, as we say now) to evaluate them in "function position" than when they weren't. I suspect he might have made that change before he got it working at all because of properties like FSUBR and FEXPR.
It was definitely dynamically scoped, though.