5.62k - a vintage original Guyatone Goldfoil pickup. These are very cool with an air coil construction - a difficult thing to recreate with most of the modern mimics of this design.
This is pretty much exactly the Ry Cooder pickup except there are not pole screws. If you wanted you could indeed drill the cover to expose the threaded holes where pole-piece screws would be inserted, though the design of this pickup never had a lot of tonal emphasis on the screws since the magnet is right under the foil itself.