[BrianG]

Example: 1512 2.5y
15 = a number that can be used to differentiate the relative diameter. Not sure if the actual number means anything, like some unit of measurement. The higher the number, the larger in diameter.
12 = a number that can be used to denote the relative length. Not sure if the actual number means anything, like some unit of measurement. The larger the number, the longer it is.
2.5 = the number of turns.
y = Delta (d) or Wye (y) motor coil formation. Delta is also called triangle, and wye is also called asterisk.