Question About Sealed Crude Rusty Bracelet (Event)

[Nanachi]

What are the chances in % to get Crude Rusty Bracelet (Event) from Burning Time Loot Box? I farmed over 100 boxes and didn't get one, so it will be helpful to know the % of getting one if possible since we can't use Dexmon Memories (Event), Yggdrasil Records (Event) or X Core (Event) except with the Bracelet from this event.