Photo-silkscreen in the Warhol manner: the same image repeated in a grid, each on a different acid flat, a black photographic screen pulled over the top, with misregistration, squeegee drag and clogged-screen blotches left in. Fine art borrowing the methods of packaging.
Pop took mechanical reproduction over the artisanal hand on purpose. The screen is a stencil, so every colour is one pull and every pull can drift, and the drift became the look. Warhol learned the basics from a commercial printer in 1961 and set up the Factory in 1964.
The rig is built once and printed as a two-by-two repeat. Each print's colour screen is translated by a hashed per-print drift, and a halftone is applied inside the black key wherever the face is in shadow, so the photograph shows through as dots.