It appears §61.55 has changed for 2007.

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§ 61.55 Second-in-command qualifications.

(a) A person may serve as a second-in-command of an aircraft type
certificated for more than one required pilot flight crewmember or in
operations requiring a second-in-command pilot flight crewmember only
if that person holds:

(1) At least a current private pilot certificate with the appropriate
category and class rating; and

(2) An instrument rating or privilege that applies to the aircraft
being flown if the flight is under IFR;

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What is the significance of "rating or privilege" ?

Thanks in advance,
ak.