An existing vessel may be deemed by the OCMI, or TPO, to be in compliance with this subpart provided that either:

(a) The vessel is built, equipped, and maintained to conform to the rules of a recognized classification society appropriate for the intended service and routes, but not classed; or

(b) The vessel has been both in satisfactory service insofar as structural adequacy is concerned and does not cause the structure of the vessel to be questioned by either the OCMI, or TPO engaged to perform an audit or survey.