The story
By June 1989, urethane had become the mainstream performance material. The Blue Knight features a polyurethane cover, confirming that every major manufacturer had fully embraced the technology that AMF and Faball pioneered earlier in the decade. The serial number 9F26640 follows Columbia's system, with "9" indicating 1989 and "F" likely indicating June. This ball was manufactured just two years before the Nu-Line X-Calibur would introduce reactive resin and change the sport again.
This ball represents the moment when urethane stopped being revolutionary and became standard. It is a "late-era" urethane ball, manufactured after the technology had been refined and widely adopted, but before reactive resin made urethane seem tame. It completes your urethane trilogy: the Black Hammer (1987, Faball), the Blue Knight (1989, Columbia), and this piece showing the technology at its mature stage.