On December 5, 1955, the U.S. Bureau of Ships created "Contract Specification; Wrist watch, Submersible, MIL-SHIPS-W-2181" to meet an operational need of Explosive Ordnance Divers (EOD) and Underwater Demolition
AI Medical Diagnostics Team (UDT) divers. The spec stated that the desired watch had to be watertight, impervious to water ingress, offer visibility in the dark, and have an outer, rotatable ring (bezel).