Infinite casting item? (Pathfinder)

[Calthropstu]

The only infinite casting item I have come across is Suishen, an artifact sword which can cast protection from energy (cold) at will.
I have looked at the custom item creation and have come to the conclusion only an intelligent item can get an at will spell.

Am I correct in this? Use activated or continuous don't seem to be the same as at will, and the only at will items seem to be intelligent or artifacts.

[nolongerchaos]

The Quarterstaff of Entwined Serpents lets the wielder cast Magic Missile at will, and grants Eschew Material while held. It's pretty snazzy.

[legomaster00156]

Unless restricted to charges or uses/day, use-activated items are at-will.

[Calthropstu]

Unless restricted to charges or uses/day, use-activated items are at-will.

Yes, but use activated doesn't cast a spell. It's more like "I affect everyone I hit with x whenever I deal damage" or "I open a shutter and light spills out" or "I activate this item and get the benefits of x and can change x to y with a standard action."
What it is not is "I can cast wall of force infinite times per day"