Terry:
Alembic are numbered sequentially, regardless of model. I believe the only exceptions may have been an Anniversary series or two. Here's the explanation of serial numbers from the Reference Pages on this site:
Serial Number Guide
The first two dgits of the serial number are the year the instrument was completed. The code letter tells you the model. The next group of numbers must be from two to five digits and is the number of the instrument. Thus 94H8692 is an Elan bass completed in 1994 and is the 8692nd instrument was made. We started with number 1 in 1972 and when an instrument is finished, it received the next number, regardless of model. Any A or B after number is on the rare occassion that we duplicate a number. Hey, even we make mistakes.
So Alembic has made less than 15,000 total instruments since it's inception. There ain't many out there - we should feel lucky to have 'em.
Bill, tgo