WHEN Big Brothers Big Sisters of the Upper Ohio Valley called Bob Dobkin's mother to tell her they found a match for her son, the good news was tempered with a bit of doubt. The "Big" they'd found for Bob was unusual - Walt Masters of Moundsville was in his early 60's and had just retired - and the organization wasn't sure it would work due to the age difference. Although Dobkin was only 11 or 12 at that time, he remembers his mother told Big Brothers Big Sisters to just let her son and Masters decide if it would work. "Thankfully she gave us the opportunity because it was a perfect match," Dobkin recalled. "It could not have been more perfect."