Spell Resistance vs Necklace of Fireballs

Question

My party just picked up a Necklace of Fireballs, and I'm trying to figure out how much damage our Drow rogue can expect to take from it. This brings up a couple questions:

1. Does spell resistance work against this item? It's not clear to me whether SR works in general against items, but since in this case it is replicating the effect of a Fireball spell it seems like it should apply.
2. What is the caster level for the fireball?

For the second question, there are a couple possibilities. One is that fireball deals 1d6 damage per level, so the caster level is equal to the number of damage dice for the fireball. The other is that the caster level is just 5, the minimum caster level for the Fireball spell. Which is correct (or is there another way to compute it)?

Answer 1

From http://www.d20srd.org/srd/magicItems/magicItemBasics.htm:

Magic items produce spells or spell-like effects.

They should be subject to SR same as the spell as if cast as normal. Fireball has SR=Yes so would be subject to it from a necklace of fireballs.

The (next) item in a notational entry gives the caster level of the item, indicating its relative power. ... For potions, scrolls, and wands, the creator can set the caster level of an item at any number high enough to cast the stored spell and not higher than her own caster level. For other magic items, the caster level is determined by the creator. The minimum caster level is that which is needed to meet the prerequisites given.

"Moderate evocation; CL 10th; Craft Wondrous Item, fireball."

So ultimately GM call to tell what level person it was crafted by to tell you caster level. Necklace of fireballs says "CL 10th" as Caster Level so going with 10th and avoiding deciding who crafted what is usually the path of least resistance. That's what we do in our home campaign.