Requested information provided below. I'm not sure how useful it will be, as InContainerID returns 0 for items/containers directly in house vault. And the ContainerID's of containers in the house vault certainly seem dynamic - They're not identical across characters.
Of additional note, .InInventory already appears to be FALSE for items in the house vault, so ISXEQ2 knows they're not in your regular inventory, I guess it knows they're not in your inventory, but doesn't know where they are so it doesn't filter them out as not AtHand. And ignore the Label field, I set that manually on the boxes so I could find them easily in the inventory dump.
An Item placed directly in the house vault (not in a container in the house vault) returns:
343: .. Fonrain, the Silent.............
Slot=3
InInventory=FALSE
InInventorySlot=FALSE
IsInventoryContainer=FALSE
IsContainer=FALSE
ContainerID=0
NumSlots=0
InContainer=FALSE
InContainerID=0
IsBankContainer=FALSE
IsSharedBankContainer=FALSE
InBank=FALSE
InSharedBank=FALSE
InSharedBank=FALSE
Label=NULL
A Container placed in the house vault looks like:
361: .. eucalyptus strong box...........
Slot=0
InInventory=FALSE
InInventorySlot=FALSE
IsInventoryContainer=FALSE
IsContainer=TRUE
ContainerID=1322998978
NumSlots=44
InContainer=FALSE
InContainerID=0
IsBankContainer=FALSE
IsSharedBankContainer=FALSE
InBank=FALSE
InSharedBank=FALSE
InSharedBank=FALSE
Label=House Vault 1
All My Containers:
House Vault:
131: .. eucalyptus strong box........... Slot(5) IsContainer ContainerID(1322999031) NumSlots(44) Label(House Vault 6)
132: .. eucalyptus strong box........... Slot(0) IsContainer ContainerID(1322998978) NumSlots(44) Label(House Vault 1)
133: .. eucalyptus strong box........... Slot(4) IsContainer ContainerID(1393463977) NumSlots(44) Label(House Vault 5)
134: .. eucalyptus strong box........... Slot(1) IsContainer ContainerID(1322998564) NumSlots(44) Label(House Vault 2)
135: .. eucalyptus strong box........... Slot(2) IsContainer ContainerID(1322998568) NumSlots(44) Label(House Vault 3)
136: .. eucalyptus strong box........... Slot(3) IsContainer ContainerID(1322999032) NumSlots(44) Label(House Vault 4)
Inventory:
291: .. Rallic Pack..................... Slot(4) InInventory InInventorySlot IsInventoryContainer IsContainer ContainerID(1418281204) NumSlots(64) Label(Inventory Bag 5)
302: .. Box of Endless Loyalty.......... Slot(1) InInventory InInventorySlot IsInventoryContainer IsContainer ContainerID(1418280984) NumSlots(52) Label(Inventory Bag 2)
303: .. Box of Endless Loyalty.......... Slot(2) InInventory InInventorySlot IsInventoryContainer IsContainer ContainerID(1417853993) NumSlots(52) Label(Inventory Bag 3)
304: .. Box of Endless Loyalty.......... Slot(0) InInventory IsInventoryContainer IsContainer ContainerID(1418281185) NumSlots(52) Label(Inventory Bag 1)
305: .. Box of Endless Loyalty.......... Slot(3) InInventory InInventorySlot IsInventoryContainer IsContainer ContainerID(1417853996) NumSlots(52) Label(Inventory Bag 4)
307: .. Naylie's Nebulous Newsbag....... Slot(5) InInventory InInventorySlot IsInventoryContainer IsContainer ContainerID(1418280983) NumSlots(66) Label(Inventory Bag 6)
Items in one of the above Containers in a House Vault look like:
78: ... Nights of the Dead Bellywhumper Battlewhiffer Costume
Slot=25
InInventory=FALSE
InInventorySlot=FALSE
IsInventoryContainer=FALSE
IsContainer=FALSE
ContainerID=0
NumSlots=0
InContainer=TRUE
InContainerID=1322999031
IsBankContainer=FALSE
IsSharedBankContainer=FALSE
InBank=FALSE
InSharedBank=FALSE
InSharedBank=FALSE
Label=NULL
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