Welcome to the Alembic Club! (again!) Keith is 100% right, doubling the measurement from nut to 12th fret is the most accurate way to determine scale length, but your bass is most assuredly a 28" scale (originally piccolo-tuned) Custom. Here is another 28" scale Custom Alembic made for standard pitch tuning- http://club.alembic.com/index.php?topic=7466.75