I’ve finally come across a way to identify the perfect date, thanks an entry from The Shepherd’s Prognostication, 1729 in my trusty Perpetual Almanac:
The nails very short, signify a person to be wicked; small and cracked to be a greedy catcher; very little, to be a crafty beguiler. White flecks in the nails signifies very wealthy, and to have many friends; black flecks, to be hated. The nails long, smooth, reddish and clear withal, to be witty and of good capacity; narrow and long, to be cruel and fierce; the nails rough and round, to be prone to the venereal act.
So there you have it. Having examined them scientifically and objectively, mine are quite clearly long, smooth and reddish. I’m just working on developing the white flecks.