As John has stated, the blades are unmarked for the L. F. & C. made variants. Original blade and skull crusher's nuts sets come up once every few months on eBay (quite regularly). There are replacement (read: new) nuts (for the Au Lion's too) on eBay now and though I have not purchased any, I doubt there is any noticeable difference between them and an original (except, perhaps condition/finish). Here's a post I did on these knives a while back The U.S. M1918 Mk. I Trench Knife Thread.
P.S. Before you inquire/ask, I do not discuss prices/values. Though you did well