TomeNET

(5.7b) The EASY_KNOW flag                                                       
-------------------------
Items that do not have any random mods, enchantments or abilities on their base
version possess the EASY_KNOW flag.
This flag means that the item will not need to be identified if it doesn't have
any special powers (ego powers/artifact). Example:

Most items don't have EASY_KNOW flag and look like this when you find them:
Dagger {+,?}    <- the question mark, hiding its level requirements, indicates
                   that you don't know if it's got special powers or not,
                   until you identify it.

Light sources are among those items that have EASY_KNOW flag and when you find
one it will look like either one of these:
Brass Lantern {+,3}   <- you know right away that this lantern has NO special
                         powers, because it shows the level requirements.
Brass Lantern {+,?}   <- you know right away that this one MUST have special
                         powers, because it masks the level requirements.

So whenever you find a light source with '?' for level requirements, make sure
to pick it up and identify it, it will have special powers!

More examples:
-Rings of Resist Fire have EASY_KNOW flag, because they cannot have any random
 properties.
-Rings of Protection do not have EASY_KNOW, because they come with a random +AC
 enchantment, so you need to identify it to find out.
-Why do Amulets of Anti-Teleportation come with '?' for level requirements,
 even though they do not have any enchantments or special powers? Because they
 have one: They can actually be cursed sometimes, this counts as random special
 power too!
-Note that shields have EASY_KNOW flag too, so make sure to pick up any shield
 that shows a '?' for level requirements, it might turn out very valuable.