I'm now even more certain about 4.
4 is a bell:
Smaller at the top, wider at the bottom - more pleasing to the eye, with a bit more drama and rakishness.
1 is a pear. Visually far less interesting.
I commit the ultimate crime of buying OTR Extra-Slim BB OCBDs (it's the only non-bespoke shirt I buy), and, to make matters worse, I don't button the buttons. I just like them. *gasp*
But, if I had a tailor with a trained hand who could concoct from scratch the perfect roll for my bespoke shirts, I would show him a picture of 4 as the model.
As for Mercer making some sort of flawless perfect true-to-history BD collar, I'd like to see them in the wild. Vox posted his shipment of 83 of them with all manner of bows and thank-you cards attached, but I think we have yet to see one in the wild.
Knowing Vox's propensity to indirectly get involved in SF discussions by posting pics that are pseudo on-point, I expect a Mercer shirt with Cambridge springtime in the background in anywhere from one to three weeks. *waits*