Hi Jim
Good question!
There have been more than 3 million of Croix de guerre awarded and probably far more have been manufactured.
The main producer is 'la Monnaie de Paris'. Unfortunately, no Croix de Guerre in bronze of WW1 has shown (until now!) a mark or a sign indicating the manufacturer.
Some have been made in silver or even in gold. Those are special products which could have a mark of the several jewellers who have made them.
Regards
Bison