#823 Serpentmen don't get additional AC when multiple bracers are equipped.
Race-specific equipment bug: in exchange for not being able to equip helms or boots and having a cold weakness, Serpentmen can equip an extra ring on their tail and two pairs of bracers (one on their forearm, and one around their thin ankles?) instead of just one pair. The problem is that when they have two pairs of bracers equipped, they only get the AC reduction from whichever pair of bracers has the highest enchantment. Equipping two sets of +2 bracers will only give you the AC reduction that you'd get from equipping one, and equipping a +3 bracers and +2 bracers will only apply the highest AC bonus, it doesn't add both their AC bonuses together.
Bracers appear to correctly apply additional non-AC bonuses correctly, for instance doubling up on bracers of magical power will increase mana regen faster than having just one pair equipped. Presumably the same applies to bracers of dexterity, etc.
I assume this is a bug and not intentional, as there's no other equipment type (rings, amulets, cloaks) that behaves this way when you double up on them (multiple AC reduction rings add the bonuses up properly).
Should be fixed in r20571.