Is there a discrepancy between the strength of aura when detect magic is cast comparing a ring of protection to a weapon with an enhancement bonus?

Question

In the SRD it states:

Protection This ring offers continual magical protection in the form of a deflection bonus of +1 to +5 to AC. Faint abjuration; CL 5th; Forge Ring, shield of faith, caster must be of a level at least three times greater than the bonus of the ring; Price 2,000 gp (ring +1); 8,000 gp (ring +2); 18,000 gp (ring +3); 32,000 gp (ring +4); 50,000 gp (ring +5).

http://www.d20srd.org/srd/magicItems/rings.htm#protection

Compare that to:

Caster Level for Weapons The caster level of a weapon with a special ability is given in the item description. For an item with only an enhancement bonus and no other abilities, the caster level is three times the enhancement bonus. If an item has both an enhancement bonus and a special ability, the higher of the two caster level requirements must be met. http://www.d20srd.org/srd/magicItems/magicWeapons.htm

So according to a strict reading when detect magic is cast a ring of protection always radiates faint abjuration (CL 5th) and the creator as a perquisite for the crafting simply needs to be of a caster level at least three times greater than the bonus of the ring created. Regardless of the actual deflection bonus of the ring, a detect magic will always radiate faint abjuration.
Whereas conversely a weapon with a magical enhancement bonus to hit and damage always has a caster level (and perquisite) three times the enhancement bonus and will 'register' as such when a detect magic determines the strength of the aura.

This would seem to be a slight but significant difference in the way these magical items are handled in respect to detect magic. Is that anybody else's understanding of this nuanced point or does anybody have a different interpretation?

Answer 1

The ring of protection (Dungeon Master's Guide 232) (2,000+ gp; 0 lbs.) has as creation prerequisites the feat Forge Ring (Player's Handbook 94), the 1st-level cleric spell shield of faith [abjur] (278), and the somewhat cryptic entry that the "caster must be of a level at least three times greater than the bonus of the ring." (This is unmentioned by official errata and unmarred by stealth errata in the premium edition Dungeon Master's Guide (2012).)

This last prerequisite means that—uniquely in the core rules—only the caster that contributes the shield of faith spell to a ring of protection's construction needs to possess a level of 3× the ring's deflection bonus—and whether this level means character level or caster level is a technical mystery (see here). (This DM would rule it means caster level, so you know.) To be clear, A ring needn't itself possess such a caster level when it's finished, and a magic craftsman needn't himself possess such a caster level to create a ring of protection.

It's this detail that causes an off-the-shelf, straight-from-the-magic-shop ring of protection to possess caster level 5, no matter the magic defection bonus the ring of protection provides. It's an arbitrary number, and why caster level 5 and not caster level 1, 12, or even 3× the deflection bonus is also a mystery. Nevertheless, a craftsman who creates an original ring of protection can still set the ring's caster level at anywhere from 1 (the minimum caster level for the spell shield of faith) to the craftsman's caster level using the general rules for magic items (see here).

While the caster level of a ring of protection doesn't need to scale like the caster level of a magic weapon that possesses only a magic enhancement bonus must, I'm not sure that's a problem… except insofar as folks like and expect patterns, and the ring of protection upsets expectations.

Answer 2

I suspect by looking at a couple of the surrounding rings that the aura given is based around the minimum caster level (also shown after aura) and not the advanced versions of the ring (which some of your examples would require a higher caster level).

For reference detect magic, note for level 1-5 items it's faint (matches your example of ring of protection) but see ring of the ram is moderate and CL9 and so on. Disclaimer: I didn't check objects besides rings.

If I am right, my guess is they did this because otherwise the entry becomes much more unwieldly, basically would need to be a table with each version of the ring (CL, power, cost) or a distinct entry per "item" (a lot more space).