Over time I'll be editing this page with more to say on filter cone design. Since even finding images of the Melitta 103 on-line is difficult (there seems to be a world-wide conspiracy to silence any evidence of it having ever existed at all), I'll just post a few pics for now.
Serious fluting is insanely absent in the upper part of many cones on the market. Sufficient fluting anywhere in the devices is a rare find. I have no idea why designers don't get this right. Superb recreational pharmaceuticals is one possible explanation. Anyway, the Melitta 103 has the best fluting of any filter cone ever manufactured, bar none.
Did I mention the huge exit ports on the thing? Whoever designed this thing knows coffee. As for the crazies who design the tiny holes "to ensure proper extraction" in so many lame filter cones on the market, I have no idea why consumers should accept the notion that having their range of control over variables (such as flow rate) arbitrarily constrained at brew-time is a feature one should be grateful for.
Proper filter folding. Yes, that's a #6. And yes, it's unbleached; I know that's worse, but they're always on sale and since I pre-heat the cone by rinsing through the filter, that single step efficiently washes out paper taste and ensures good serving temperature for the brew.