Unfortunately, the maker's marks were usually ground off the rough forged tubes when the tubes were joined, fit, and finished. To my knowledge, the only mark found to date has been the "HRF" of Heuse-Riga Fils on a Flues, but it is very likely tubes were sourced from other Vesdre valley makers
More infro here https://docs.google.com/document/edit?id=17yCstxftvWXpFdSru4JKbRIE1-Q8OqXgJs66tEXntqw

Examples, mostly courtesy of Bro. Walt, are here
http://www.picturetrail.com/sfx/album/view/20991622


Last edited by Drew Hause; 10/26/12 05:22 PM.
https://sites.google.com/a/damascusknowledge.com/www/home