Just saw this from Scoot on the Track forum. Second 2 numbers in the name signify MB strength....here's a cut and paste:
the 5 7 9 series are the numbers that will be used to tell what line the ball is in.
5 Series is the Mid performance line
7 Series is the Upper - Mid performance line
9 Series is the High performance line
each series will have its number in the name. Then you will have a number that tells you the core strength of ball in the line. Finnally in the name you will have one of three letters that will tell you what kind of cover the ball has. The letters will be C = control, A = Angular, T = Traction. Each letter tells you something. C tells you the ball will be smoother overall and is a good benchmark type ball. A tells you the ball will get down lane and be ideal skid flip. T tells you the ball has a cover made for oil. So with these lets create a fake ball to give you an example. We will use the 7 series for this.
The name of the ball we will use will be 724T.
What you can take from this name is the following.
1. It is a 7 series ball
2. The core strength (MASS BIAS STRENGTH) is .024
2a. Each series has a set number that the core strength will be in. For example the 5 series will have mb rating from .0000-.009. The 7s will be .010-.024, and the 9s will be .025 and higher.
3. The type of cover on this ball is ment for oil.