Yes, if you have been in the wrong retirement plan for at least 3 years of service AFTER December 31, 1986.
It does not matter that your agency may have already corrected the error or that you have retired or no longer work for the Government. As long as the error was in effect for at least 3 years of your Federal service after December 31, 1986, then you may benefit from FERCCA.
FERCCA may also affect you if you were put in FERS by mistake and can make, or made, what we call a "deemed FERS election". You don't have to be in FERS for at least 3 years to benefit from FERCCA. See the question, My agency put me in FERS by mistake. When it discovered the error, my agency let me choose whether I wanted to remain in FERS. Do I get another choice under FERCCA? for an explanation.
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