There is a discrepancy between announced probabilities of spawning the nautilus armor and rate which I experienced looting buried treasure chests in my world. The world was created almost a year ago and went through all this year's updates. I tried to find diamond armor, simply looting buried chests. I found and opened over 200 chests (in creative mode), and stats are: less than 10 copper armors, about 5 iron ones, 1 gold one and literally none diamond armor.
MCPE-233434
Nautilus armor has low spawn rate in the world created in previous versions of MC
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My world is 2 years old. I’ve found 16 copper nautilus armour, 15 iron, 3 gold, and zero diamond after going through 180 buried treasure chests, so iron seems to be over represented, and I must be getting insanely unlucky for diamond.