Which New York Yankees baseball player autographed the back of Stevie Ray Vaughan's "Lenny" guitar in 1985?

Lenora "Lenny" Vaughan, Stevie Ray Vaughan's wife, gave this guitar to her husband on his 26th birthday (Oct 3, 1980) ... Vaughan was invited to play the national anthem at the Houston Astros season opener, against the Los Angeles Dodgers at the Houston Astrodome on Wednesday, April 10, 1985 ... Mantle was at the game to throw the first pitch; it was pure chance that Lenora found herself standing next to one of the greatest baseball players in history. When Stevie joined her minutes later, she introduced the two men."I don't know how to play that song," Vaughan confided to Mantle, to which the Yankees great replied reassuringly, "Nobody can play that song." Lenora then sheepishly asked for Mantle's autograph, upon which Mantle asked where her baseball bat was. "Oh... oh... am I supposed to have a bat?" she stammered. Mantle explained that most autograph seekers bring a bat. Lenora remembers that "I was looking around for a piece of paper of something, and Stevie said, 'Well I've got this bat right here - her name's Lenny.' And he took it out and said, "Why don't you sign this?' And Mickey said, 'It'd be my pleasure.'"