The OP's seat sounds completely legal as it carries the right homologation (certified 03/2001)and it has NOT been withdrawn.

My editorial was because the GCR specifically calls out FIA 8855-1999 and 8862-2009 seats. there were standards before that which are no longer recognized, and a seat homologated to one of them is no longer acceptable as an FIA seat. Also, eventually SCCA MIGHT enforce the 5yr expiration, and eventually 8862-2009 or some other standard will supplant 8855-1999 as that recognized, and existing seats will likely be phased into expiration at that point. Not really what was asked but added info.