The potential for two Offerings?!

When you have Gau Leap on the Veldt, whatever equipment he was wearing is flagged as being not equipped. If it's an item you only have one copy of, you can then equip it to another party member while Gau is gone, and then Gau will still have it equipped when he returns.

This doesn't increase the actual number of copies you have of that item: It just allows two party members to equip the same item.

Here you can see that my inventory contains -1 Earrings, Hermes Sandals, and Ninja Gear, all of which I have one copy of, but that one copy is being worn by both Gau and Sabin.