The ETA 1004 watch movement is a hunter calibre with options including a bimetallic screw balance and a Breguet hairspring. It comes in different construction heights, specifically 4.1mm, 4.75mm, and 5.0mm, with various bridge shapes available. These calibres are not extensively documented in literature, but variants known from literature and real-world examples are listed. The movement features stem winding and setting, a sub-second hand, and was used around 1928.