Switch to Luminova happened halfway the B-Series (= Millenium Change).
Was the same moment that the OP6502 case reference split up into OP6518 (SS Marinas = PAM 1 3), OP6519 (PVD Marinas = PAM 4 and later 195), OP6520 (SS Base = PAM 2 & 10) and OP6521 (PVD Base = PAM 9) and the OP6504 reference split up into OP6522 (SS Destro = PAM 22) and OP6523 (PVD Destro = PAM 26).
As with all things Panerai, there are exceptions, but if you own a B-series Historic with the OP6502/6504 case reference, there's a 97% chance that it will have a Tritium dial. If you own a B-series Historic with an OP6518-6523 case reference, there's a 97% chance that it will have a Luminova dial. If all the owners of B-series now respond with stating their case reference, PAM-reference and dial, we can do some statistical mathematics and determine if those 97% are more likely 99% or 95% or 90%.
Pinpointing this at the end of 1999 (= halfway the B-series) doesn't necessarily mean that we won't find OP6518-6523 watches with Luminova dials that were already sold in 1999. They usually finished the watches in batches (can be 10-20 pieces for a given PAM-reference to several hundreds in 1 run). Possible that they finished a first batch of watches using the new cases and new dials when these became available, whereby they later continued doing other batches using the old cases and old dials. The BB-numbers can provide some input there.
1500 is the total for all B-series Luminor Base models, includes references OP6502, OP6520 and OP6521. Asi was once able to get a look at a Panerai Marketing Communicazione Note for ADs and the split-up was 700x PAM2, 400x PAM10 and 400x PAM 9.
For the B-series Luminor Marinas (3000 pieces), the split-up was 1500x PAM1, 699(!)x PAM 3 and 800x PAM4, covering OP6502, OP6518 and OP6519 case references.
Want to know the split-up for A-series OP6502? Here they come:
Luminor Marina: 900x PAM1, 250x PAM3 and 350x PAM4
Luminor Base: 500x PAM2, 250x PAM10 and 250x PAM9
B-series starts round the BB978000 mark and stops round the BB992250 mark.