Part 25 (JAR/FAR) are two sets of very similar design and certification standards.
The simple answer to your question is, if it is certificated to Part 25 then it is a Part 25 aircraft.
The test, for example with FAR 25, is to check the FAA
TCDS for the particular aircraft .. is the aircraft listed there ?
So, for instance, the EMB-120 is a
Part 25 certification.
If I recall correctly there are some links to JAR data in the tech log URL sticky.