An early release, (with 2 other blacks) this was an important "cold" black.  The cold tone of the blue allows it to work well with blues and greens while the warm tones of the Black Violet, 974 works well with reds, oranges and other "hot" tones.  Well, that was the thinking when the colors were first introduced; the reality is that people use the one they like and this one is well liked.  An easy working, opaque black!

Working Tip: Work in neutral flame to avoid reduction (gray streaks).