You can get them starting from Delphi Temple all the way to Vilespire Temple 0/10. After Vilespire Temple, 0/10 dungeons stop dropping Seal Stones and instead have a chance to drop a guild boss summon scroll.
And just like the description, you can get them from treasure maps starting from Delphi Temple treasure maps and above. I don't believe 75+ maps have a chance to give them though but this is hard to test as you can imagine.
Game = Eden Eternal. Server = Server merged server name. Old server = Sapphire. Old server = Garnet. Guild = Objection. IGN = Zetsumei418. Old IGN = [GS]Kuma. Old IGN = Zetsumei418