The story
The Black Knight is a straightforward polyester plastic ball with a pancake weight block—the standard entry-level design of its time. Pancake weight blocks are simple, symmetrical discs that provide minimal performance tuning but are cheap and easy to manufacture.
By December 1987, urethane balls had been available for six years, and the first reactive resin balls were just a few years away (the Nu-Line X-Calibur launched in 1991). Polyester balls like the Black Knight were increasingly seen as spare balls or beginner equipment, while serious bowlers had moved to urethane.
The serial number 7L53970 follows Columbia's dating system, with the "7" indicating 1987 and the "L" likely indicating December. This ball was manufactured in the same year as your Black Hammer, but represents a completely different market segment.
This ball captures the moment when polyester became "basic" rather than "advanced." It contrasts beautifully with your 1987 Black Hammer, showing how two balls made in the same year could represent completely different levels of bowling technology.