The flange material is ASTM A694 Gr. 52 (or another grade), and to use ASME B16.5 to specify the flange class, I do not know what material table corresponds to this material. Can somebody shed light, please.
Consider checking the ASTM web site for the title of A694. Also try a Google search listing ASTM A 694 and "UNS". However a quick check for "694 in B16.5 found nothing.
ASTM A694 / A694M - 08 Standard Specification for Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service
ASME Standards
ASME B16.47 Large Diameter Steel Flanges