SOLUTION FOUND: In the my material, the Standard Material Node - Advanced Tab, there is an option under REFLECTION, End Color. It looks like the default is set to Environment, for my purpose Diffuse behaves properly.

Cheers.

Metallic material, highly reflective. Hollow object or concave with internal self reflections... camera looking in. During testing I turned EVERYTHING off in dome light Details but the internal reflections persist!?!?! (sorry, up-to-date Redshift and C4D) Am I missing something or could this be a bu...