John - The new book by Chris Curtis "System Lefaucheux" has a very complete listing of marks and dates on pages 208-215. There are several pages of various marks.
The marks are usually in the frame above the triggerguard. You have to also know that these can have other marks. French and Belgian being most common - but English, Spanish, and German marks are also listed.
Then there are some really funky oddball copies from who knows where . . . .
This new book is a must have for a serious collector.
Hope that this helps - Gene