It's custom made for Suhr to the exact recipe that Fender used in the early 60's. The magnets used for pickups to chip when they were cut, so Leo had to pay people to grind the magnets. It's why Strat pickups and Tele neck pickups have covers. They weren't pretty. To combat this, they changed the formula so that the magnets weren't as brittle when they cooled. This also changed how they sounded.
When John was a senior master builder at the Fender Custom Shop Jeff Beck asked for them to make him some pickups like in his old '63 Strat, and they went through multiple batches and couldn't do it. John figured out that the magnets were different, so he tracked down the original supplier and asked if they still had the formula that they used for Fender in those days. He ended up chatting with a guy who still worked there who was around in the early 60's and they were able to recreate it. That's the Alnico V special. Suhr guitars are currently the only ones with that magnet, which is why their singlecoils are about as dead-on a recreation of the early 60's Fender pickups that you can get.