Thanks Craig,
Your answer and analysis was right on the mony$$. The BASIS reps. answer was almost a copy of yours, albeit with a more detailed explanation and screenshots to boot.
Now we'll simply have to search out QDLs and associated historical changes in a different way,IE, it can't be expected that batches will be issued in sequential order. Our batch number holds 50 numbers.
Much Thanks for your early on help...
Verroz