I have discovered among the files for “misc” items for France (“misc” texture folder is for deck clutter items mostly) there is a file merely labeled “FM417_Jean_Bart.dds”. The texture file itself appears to merely contain the textures to various items such as windows and possibly a range finder, that must belong uniquely to the Jean Bart.
If you have the WOWS_UNPACKER program for the client, the file can be found here: res/content/gameplay/france/misc/textures/FM417_Jean_Bart.dds
(This would not be the first instance of files that were not meant to be in the client accidentally being released, assuming its an accident due to the lack of any other texture pieces for the ship.)
Discovered by myself, Shipmaster_Crook.