Here's a Lefaucheaux Action W. Richards, but I don't find 'DD' on PeteM's list of marks

DD in an oval lying was used by Jean Delcour-Dupont de Fraipont-Nessonvaux
Unless I can find independent documentation, the mark doesn't make it onto the list. There were simply too many maker's marks that are still unaccounted for.
On occasion I send things to Alain at LittleGun to be sure. I wish I could provide more information for each maker/mark. As it stands with over 1,000 confirmed marks, it is the most concise listing I am aware of. If I had a couple weeks I know I could add a few hundred more by digging into catalogs and other documentation I have.
Recently got a listing of hundreds of makers marks through out Europe, mostly 16th, 17th and 18th century, "Marques D'Armuriers". It will be a long time before I get that info online. I will have to scan every mark from that one.
I am hoping for even more soon from a newly formed research group in Europe.
Pete