You can tell the Japanese and Joustra Battle Convoy apart from the colour of the parts on the trailer. The Japanese Diaclone has very light blue parts on the trailer (especially underneath). The Joustra will have a darker blue much like a pre-rub Transformers Prime would have.
Some very very early Transformers Optimus Primes have the same light blue parts (but not the metal plates, only grey-roller Prime has the metal plates)
Also, the Japanese Diaclone should only say "TAKARA JAPAN" on the copyright. The Joustra might well have dates and Japanese writing as well.
All the best
Maz
