What is upper limit for +ED on rare weapons?

I found a rare tyrant club with +443% ED. Until then, I had believed +ED on a rare or magical weapon was capped at 300%, but obviously it isn’t. What is the maximum possible %ED on a rare weapon?

It has a combination of both the “+ Damage” and “+ Attack Rating and + Damage” Prefixes.
http://classic.battle.net/diablo2exp/items/magic/pre.shtml

+ Damage

Merciless +81-100% Damage Weapons(32)
Ferocious +101-200% Damage Weapons(41)
Cruel +201-300% Damage Weapons(51), Weapons(56)

+ Attack Rating and + Damage

King’s +121-150 to Attack Rating, Damage: +81-100% Weapons(56)
Master’s +151-250 to Attack Rating, Damage: +101-150% Weapons(56)
Grandmaster’s +251-300 to Attack Rating, Damage: +151-200% Weapons(69)

I think max ED on a rare wep is like 430 or 450% ED

You can double roll damage mods like Cruel > Master’s > Mechanics “Berserker Axe” of Quickness > Self Repair > Carnage.

This roll would be about the highest damage you could roll on a weapon assuming stats are perfect.

On Arreat summit you can roll Cruel and Master’s on a rare weapon so 450% ED would be perfect.