SYSP

[kmp at MIT-MC (Kent M. Pitman)]

(SYSP x) returns a non-() value if x is a symbol which has a system SUBR,
 LSUBR, FSUBR, or AUTOLOAD property. It also returns non-() if x is of typep
 RANDOM and is in the range of the binary program space of the initial lisp 
 system. Otherwise, it returns NIL. It makes no claim to tell you if the
 functional property in effect is the system version.
eg,
	(DEFUN LOAD (X) X)    => LOAD
	(LOAD 'FOO)	      => FOO
	(SYSP 'LOAD)          => SUBR
	(REMPROP 'LOAD 'SUBR) => (#...)
	(SYSP 'LOAD)	      => NIL

-kmp