Greenfield
Adventurer
If the claws give a Grapple bonus as a normal use of the weapon, I'd allow it even if you aren't proficient with the weapon, as such.
Of course, I'd apply the -4 non-proficiency penalty to any maneuvers (including Grapple) you attempted with the weapon, just as I would if you were trying to use it to Sunder, Disarm, Power Attack or anything else.
There are a few items that give you bonuses just for possessing them. Very few of them are weapons, and none of those bonuses apply to weapon use or maneuvers with any other weapon.
Of course, I'd apply the -4 non-proficiency penalty to any maneuvers (including Grapple) you attempted with the weapon, just as I would if you were trying to use it to Sunder, Disarm, Power Attack or anything else.

There are a few items that give you bonuses just for possessing them. Very few of them are weapons, and none of those bonuses apply to weapon use or maneuvers with any other weapon.