Black label are limited (but continuous) production, with only a maximum of 2 per boutique and capped to 12 total per year for a given model. They were originally intended to be further limited to those who already have at least one FPJ, but I know of cas...
That is 20 pieces for one model. In total however, if you had 10 boutiques that means a max of 120 black dials per year. It doesn't becomes 1 of 2 once you run the numbers lol
I was coincidentally in contact with the Paris boutique yesterday- so I asked them specifically about your question. The rules are: 2 pieces of each model can be ordered pr year at each bouique. Since there are 9 boutiques there could theoretically be 18 ...