Given that the klar is basically an animal skull with a curved blade protruding from the area of where the upper jaw would be, I would say no. It's probably slashing only as the entry indicates.
Though if I recall correctly there is more than 1 entry (across various sources) which contradict each other on how it works.
If you look up the picture of a klar, the blade is lightly curved despite not being indicated in the descriptive text, which is where they most likely are getting the slashing damage from.
In sources that list the weapon, it appears that the only list it as having slashing damage not piercing.
It is unclear exactly what it's supposed to me that "a klar counts as a light shield with armor spikes".
However, my take on it is that you can enhance it as both a weapon and shield and that it normally provides a +1 shield bonus without any enhancement like a light shield would. And that the weapon part counts as a light weapon.
They've revised the weapon several times, but have never clarified it or ever added piercing damage to the description line in the entry (that I saw).
Which leads me to think that no, you can't do piercing damage with it.
But I'm not sure there is anything official to answer your question.
KLAR
Price 12 gp
Shield Bonus +1
The traditional form of this tribal weapon is a short blade bound to the skull of a large horned lizard, but a skilled smith can craft one entirely out of metal. A traditional klar counts as a light wooden shield with armor spikes; a metal klar counts as a light steel shield with armor spikes.It doesn't say curved, but it does reference armor spikes that deal piercing damage. So could I attack with the Klar, or serparately, attack with the armor spikes?ARMOR SPIKES
Price +50 gp
Armor Bonus —
You can have spikes added to your armor, which allow you to deal extra piercing damage on a successful grapple attack (see "spiked armor" in the Martial Weapons Table). The spikes count as a martial weapon. If you are not proficient with them, you take a –4 penalty on grapple checks when you try to use them. You can also make a regular melee attack (or off-hand attack) with the spikes, and they count as a light weapon in this case. (You can't also make an attack with armor spikes if you have already made an attack with another off-hand weapon, and vice versa.) An enhancement bonus to a suit of armor does not improve the spikes' effectiveness, but the spikes can be made into magic weapons in their own right.
The weapons table tells you exactly what damage it is. Light shields with armor spikes generally do piercing damage but specific trumps general and the table specifically says it does slashing. So it does slashing and, because it counts as a light shield with armor spikes (notice it doesn't say it IS a light shield with armor spikes), you can use any feats that normally apply to light shields with armor spikes.
Both of you put forth exactly the points of view I had originally when I was looking at it. I was just trying to play devil's advocate to get extra value. Thank you both for concisely answering my question.
Gotta be careful advocating with them devils! They are sneaky bastards! Especially those Erinyes. Don't believe them at all when they try and get you to let them tie you up with their ropes. It never ends up being as fun as it sounds.
We try to help.
Sorry there isn't a more definitive answer.