This is the 2022 edition of the Massad Ayoob collaboration model, which has achieved such a cult following over the years that there was enough demand to revive the model for two separate sprint runs after its original discontinuation in 2002. 

Aside from the general scuffs and scratches, most these units were "2nd'd" for the serration pattern. For this model, they tried a new serration pattern but near the tip it ended up not looking the way they wanted, so a very large portion of the finished batch ended up getting held back and sold as seconds. This particular 2022 Sprint Run was overall quite an ordeal for Spyderco to produce and as a result they might not make this model ever again. Here's the story as told by Sal on Spyderco Forums:

We began working with this maker in 1988. At the time, they were considered by most experts, even in Japan to be THE premier quality knife maker in the world. It is/was a small family business consisting of the "Old Man", who was the driving force. He had more than 80 patents on his designs and they produced a small number pieces.

The "Old Man's" wife handled the office. There were two sons. One handled sales (#2 son) and one handled the factory with his father (#1 son). His wife also helped with the office.

Then one day, with no warning, the Father had a stroke and was no longer able to work. The Father's wife had to stop working to take care of the Father. Now the sons are running the company with the Patriarch and the Patriarch's Wife no longer involved. Very challenging, even devastating. They had one major lower quality customer (A Hardware chain) that carried the company. A few special customers like Spyderco and their normal consumer direct line.

Then "The Rains came". In one year, the Father passed away. The Mother passed away. #1 son had a stroke, and #1's son's wife passed away. Now the Grandson is running the factory and he really wasn't ready. Then the main Hardware chain found a less expensive supplier. The family was devastated.

We brought the Grandson to our factory in Golden to try to get him better trained and brought into the 21st Century manufacturing. Ir has been a long road and they are beginning to get back on track which pleases us and we're helping.

All of the people that headed up and made the original model 11 years ago are no longer alive, and this project was a major mountain to climb just to be able to make them. We're very proud of their achievement in this Sprint, while not perfect, is a major milestone in their rebirth. Those of you that are disappointed, you have my apologies, and if you are not pleased to accept the "funky tooth", you should return the piece and let someone else have it. We will not likely make this model again as we encourage and help the family restore their skill.

If you're interested in learning more, check out the Spydiewiki page about it. Here's some design insight from Massad Ayoob himself that I found on the spydiewiki page (originally from Bladeforums):

The rationale was to get the blade directly in line with the radius bone of the forearm when the average human wrist was in the "locked" position, which puts the middle knuckle of the hand directly in line with the axis of the forearm.

This is what gives the C60 its superior stabbing accuracy that posters in this thread have mentioned, and it also gives tremendously more penetration, because it aligns the skeleto-muscular support structure of the arm with the point (number one), and therefore with anyone who knows how to put his weight behind a punch, gets the entire body's force going directly behind the point (number two).

As other posters have also noted, the handle-to-blade angle puts much more force behind a slash as well as a stab. Instead of the blade "skimming" over the target as it hits hard resistance such as bone, the 90 degree angle of the blade when held in reverse grip (and KEPT there by a handle shape that allows the thumb to lock it at that angle) the C60 is more likely to shear directly through whatever resistance it encounters. Because of the design features, something very similar happens with a slash from the conventional saber or pekal grasp.

As to the tip-down carry: I'm one of those early Spyderco fans whom Sal calls "Clipiteers," [:-)] who started their Spyderco experience with the original Police model, learned to open it with a pinch-snap, and discovered we could win bets beating guys with bali-songs and even "automatic knives" in opening speed. The pinch snap uses the gross motor movement of the closed hand instead of the more fine-motor skill of using the thumb to open the blade via the original design intent of the "Spyder-hole."

As has also been noted (you guys n' gals are sharp, no pun intended) the C60 had ambi holes drilled so the clip could be moved for southpaws. I did not consider tip-up carry in the design parameters, and would have to go back and play with the concept a lot more to see how well it would work in that fashion. I realize that a lot of folks are as habituated to tip-up carry as I am to tip-down.

While it is unconventionally shaped with the negative blade angle and features serrations, I still highly recommend it as a "surprisingly great" EDC choice. With a Sharpmaker, sharpening serrations really is not a challenge anymore. Give it a try, I bet you'll be impressed with the craftsmanship, materials, and performance of this unique, long gone limited edition model.