For every 100 abbreviated ball park signatures that Mark McGwire signs, there is perhaps one full signature that he reserves for close friends and Major League Baseball employees. Because of this, finding a full McGwire signature on a premium item such as a jersey or bat is very difficult. This full Mark McGwire '01 black Sharpie signature on the back number 5 of this St. Louis Cardinals red Majestic McGwire warm-up jersey unquestionably rates a near 10. The autographed jersey comes with a PSA/DNA letter of authenticity.