Dirk has also posted this as well, however...
There's no way to tell if the watch has a T SWISS T or T-SWISS-T dial based on the serial and millesimation number (you just need to look at the dial, the shape of the indexes and what's written below the 6).
Here's how to tell if a watch is a real pre-A.
There must be a logic relationship between the serial (BB) and millesimation number in all 3 cases.
OP6500 are PAM 1-2-3-4-9-10 that were produced before the insertion of the 400x OP6501 Mare Nostrum serial numbers.
The last 4 digits of the serail number must be the same as the last 4 digits of the millesimation number.
Example:
BB970305
0305/1000
OP6502 are PAM 1-2-3-4-9-10 that were produced after the insertion of the 400x OP6501 Mare Nostrum serial numbers. Impossible to date to determine the precise point where OP6500 stops and OP6502 starts, as the OP6501 doesn't have a millesimation-number.
Without A-prefix: the serial number is 400 higher than the millesimation number.
Example:
BB971295
0895/1000
With A-prefix: the serial number is 1400 higher than the millesimation nuber and Marina-models retained /1000 as suffix. Ends somewehere below the BB971700-mark.
Example:
BB971539
A0139/1000
A couple of genuine pre-A watches have been observed with T SWISS T dial (can be a dial switch/upgrade during service or a pre-production prototype) and T-SWISS-T dials were observed on a dozen or so later normal A and B- series watches.
The bolded text above is the basis for my inquiry