I find several things that make the early Fenders different from the CBS pickups made after 1965.

The early Fender pickups had much more hand work and unique sounds. The bobbin was mostly black Vulcanized fibre flatwork. The magnets were a larger diameter (.197″) and the CBS pickups used a (.187″) diameter magnet. The magnets were hand ground on one end to help with bobbin assembly. The larger magnets had a rougher sand cast surface that held the bobbin firmly. The early coils were hand wound and CBS coils were wound several at a time. The early bobbins used a wax with lamp black to help eliminate unwanted feedback.

Some of the mid-60s Telecaster bridge pickup were not wax potted, which caused a high amount of microphonic feedback especially when playing at higher volumes. Leo told me that by hand winding pickups, you can feel the winding tension better between your fingers. Leo liked hand winding for the tone he wanted out of his pickups.