One of my contentions about the D&D rules is that there are a number of areas where Gary Gygax failed to give a rule because it was in a previous edition of the rules. Thus, you require CHAINMAIL to use a lot of original D&D, and there are a number of areas in AD&D that aren’t described because the rules are in oD&D.
Item Saving Throws are one that have caused trouble over the years. The AD&D DMG gives the rules for how they make or fail the checks, but doesn’t actually say when to make the checks. So, we’ve seen over the years versions like “every time you get hit”, “when you fail a save” or “when you fail a save with a natural 1”.
However, the original D&D rules give guidelines as to when to use item saving throws! Monsters & Treasure, page 38, reads, “Magical items will, during the course of play, be struck by various forms of weapons. For the sake of simplicity, it is generally easier to assume that they survive unharmed if their wearer/user is not killed (exception, Helms). If the wearer is killed, or the items are alone, throw for them on the following table…”
AD&D 2E gave the rule as “when character failed saving throw or unattended”, but – for various reasons – I prefer the oD&D rule and will be using it in my AD&D game.