1940s Eterna Big cushion staybrite 38mm water-resistant Black gilt dial "Engrave back"

This is a rare 1940s Eterna Big Cushion Staybrite 38mm waterproof watch with a black gilt dial and an engraved back. It is a civilian model of the Big Cushion model adopted by the Czech military. It features a 38mm screw-back waterproof case made of Staybrite material, the in-house Cal. 852S movement that covers the entire mechanism, and a highly legible black gilt dial. It is an attractive piece with high practicality and design similar to military models. The case back is a rare early engraved version, different from the later plain versions.