I think the 200K number is 'Hy'. The 700's had serial numbers with first digit "7" and the highest of those I've noted is less than 703000. When they started with models 80x it appears they commenced at 800000 and the highest I've noted is around 935000. If they didn't skip any numbers we might expect around 140 or 150K total production.
Surely the highest production numbers of all would be for either the Marksman cheapo or some version of the GAT pistols; either of those likely sold in the millions.
If you limit the race to "quality adult" pistols, some contenders would have to be Diana 5, Webley Tempest, and maybe other Webley models?
Don R.