Hello
If it was a car transporter or a horse trailer it would be simple!
Why? It seems that "Horse trailer" is unknown in box J3 !
However, if you were a cattle breeder, you could write in J3 - BETAIL (
ie cattle).
http://www.carte-grise.org/docs/List...12-06-2009.pdf But unfortunately, it does not apply to trailers, only for trucks

You're welcome...
My best choice:
box J1: RESP (REmorqueSPécialisée)
box J3: NON SPEC (NON SPECifiée)
Hope this will help.
NF