Think you'll find it is a Reverse Buckling Disc. Io ensure it is assemble correctly, the disc is held between the holders by the 'Side Strap' which should indicate the direction of flow. This is so done as to ensure proper installation in the direction of flow. See attached. Most discs now being self rupturing are installed the over way.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.