This is a U.S Pattern Hybrid Military Watch strap which whilst made from similar nylon webbing material to European NATO straps but is simpler to wear and sometimes preferred even by serving UK personnel although it combines some of the advantages of European NATO straps, it is based closely on the U.S US military watch strap covered by, MIL-S-46383A1 WRIST: INSTRUMENT June 1965.
1.2 mm thick premium quality ballistic nylon
High Quality stitching
Fixed nylon loop in compliance with in compliance with U.S Military Specification MIL-S-46383
