The plot thickens-may have found a c. 1870 Parker with 'LD' for Dumoulin-Lambinon (1860-1879)
http://www.littlegun.be/arme%20belge/artisans%20identifies%20d/a%20dumoulin%20gb.htm This is what I've got so far:
DamascusL.C. Smith: Bauduin Doyen & Jean-Baptiste Delcour-Dupont
Baker: Charles Spirlet & Arthur-Delvaux-Heuse
Lefever: Arthur-Delvaux-Heuse & George Laloux
Fox: Jean-Baptiste Delcour-Dupont
Ithaca (Flues): Heuse-Riga Fils
Steel Laurent Lochet-Habran: Smith, Lefever, Fox & Ithaca
Please check your classic American SxS damascus brls for other maker's marks and let me know and thanks!