Hello, Bkcdfish.
I have 8 of the Lefaucheux 12mm M1854 revolvers in various styles and they are all basically the same. The M1854 "Navy" model does not exist as such - it is a M1854 without the finger spur, but there is no indication that it was made for the navy. However, there is a M1858 Marine model made at Ste. Etienne - and only those marked as Ste Etienne guns can be called "marine". Lefaucheux was allowed to continue to manufacture the same model for civilian sale, but it was still a M1854. Getting parts is virtually impossible unless you can find a "beater" to salvage parts from. Making the parts can be done, but that will be tough, too. Send me an e-mail and I will take some pictures for you.