Table 1
Table 2
Table 3

MAGICAL ITEM PLANE-OF-ORIGIN TABLES

Note: Not only can these tables be used to determine the plane of origin for weapons and armor, it can also be used to add flavor to other miscellaneous magical items. For example, a ring of invisibility made on Baator might be made of green steel with a ba'atezu's eye for a gem, while a similar ring made on the Elemental Plane of Water might be made of delicate coral, carved into the shape of breaking waves. 

"Present plane" is the plane of discovery; more often than not, items are found on the plane where they were made. For example, if the adventurers discovered a wand of fire in Sigil, and the DM rolled a 46 on Table 1, the item would be Sigilian in make.

Note that on Table 2, the planes of extreme alignment (Mount Celestia, Baator, the Abyss, and Arborea) are weighted heavier than other Outer Planes, and the planes of neutrality (Sigil and the Outlands) are weighted even heavier than those. This was done to reflect the natives of the planes of extreme alignment producing more magic (notably the Abyss and Baator for the Blood War) and the popularity of items forged on the Outlands and their ability to be used equally well everywhere on the Outer Planes.

Table 1
01-50 Magical item was made on present plane
51-90 Roll on the appropriate table (Table 2 if the present plane is an Outer Plane or the Astral Plane, Table 3 if the present plane is an Inner of the Ethereal Plane).
91-95 Roll on the converse table (Table 3 if the present plane is an Outer Plane or the Astral Plane, Table 2 if the present plane is an Inner of the Ethereal Plane).
96-00 Magical item was made on the Prime Material Plane

Table 2: Outer Planes and Astral Plane
01-04 Mount Celestia
05-06 Bytopia
07-08 Elysium
09-10 The Beastlands
11-14 Arborea
15-16 Ysgard
17-18 Limbo
19-20 Pandemonium
21-24 The Abyss
25-26 Carceri
27-28 The Grey Waste
29-30 Gehenna
31-34 Baator
35-36 Acheron
37-38 Mechanus
39-40 Arcadia
41-48 Prime Material Plane
49-56 Astral
57-60 Roll on Table 3
61-80 The Outlands
81-00 Sigil

Table 3: Inner Planes and Ethereal Plane
01-08 Air
09-16 Earth
17-24 Fire
25-32 Water
33-36 Smoke
37-40 Ice
41-44 Ooze
45-48 Magma
49-50 Lightning
51-52 Steam
53-54 Radiance
55-56 Mineral
57-58 Vacuum
59-60 Salt
61-62 Ash
63-64 Dust
65-66 Positive
67-68 Negative
69-88 Ethereal
89-96 a Demi-Plane
97-00 Roll on Table 2