SYSP

[EB at MIT-MC (Edward Barton)]

    Date:  5 FEB 1981 1220-EST
    From: kmp at MIT-MC (Kent M. Pitman)
    Subject: SYSP
     It makes no claim to tell you if the
     functional property in effect is the system version.

According to the old LISP manual, it DOES make such a claim.
From that manual:

sysp                SUBR 1 arg

     The sysp predicate takes an  atomic symbol as an argument.  If  the atomic
     symbol is the name of a system function (and has not been redefined), sysp
     returns  the type  of function  (subr, lsubr,  or fsubr).   Otherwise sysp
     returns nil.