In any case, the 5091 and its derivatives were part of a run of about 2-3,000 watches in total. I'm pretty sure that any individual variant would have been produced in no more than a few hundred pieces. Caliber 315 SC, I believe. It was reported long ago that the 5091 and its variants were a custom-run for a Patek Philippe distributor in Russia during the late nineties.
Best,
Tim