>>280731576
It's never mentioned where it came from. We know how it works because of Pagaya from Skypia, of it's existence and more from Smoker in the Alabasta saga (Starting in Loguetown and into the Crocodile prison). It's used around the world, but only really by the marines and powerful criminals like Crocodile (Whose plan mirrors Doflamingo's and is shown to know how to work in the Underworld with Cross Guild)
We just assume this is something the government mines and produces given how many Battleships the series has thrown at us from non-canon sources and the few massive battles where a Marine ship is destroyed.
We have never been shown Seastone being used in any glimpses of the past 27 years plus (Orochi was shogun and working with Kaido 26 years into the past). We can remark this as well that the 'Decommissioned Battleship Bags' are the same ships that would have a Seastone bottom, a material that is as hard as diamond, but are clearly beaten away at. Which implies either Garp can mold diamonds with his fist OR they were decommissioned due to not having Seastone from Wano.
In all honesty, the issue is 'Weapons' and 'Seastone'. Oda kinda needed to explain how those connect because we only get "Oh, They are making normal weapons and also they are the origin of Seastone. That thing the government and master criminals use a fuckton of (Moria didn't have them, It's unknown in the East Blue, Don Krieg didn't rock any. Crocodile was the first criminal to have it)
