45.22(b) allows any aircraft built at least 30 years ago to display 2” numbers or. An experimental exhibition or experimental amateur built aircraft with the same external configuration as an aircraft built 30 years ago (replica) to display 2” numbers. Same external configuration means exactly the same, not a scaled down or scaled up version.
I can’t say when the last 180 or 185 was built, but suspect they are all over 30 years old.
If you are an Experimental Exhibition or AB, and meet the “same external configuration” as an aircraft that was built 30 years ago and you display “NX” with your registration number it eliminates the 2” “EXPERIMENTAL” placard requirement by the entrance to the aircraft.
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