The Belgian steel industry has English roots. In addition to Cockerill, in 1830 Thomas Bonehill set up a forging mill.

http://www.cockerill-sambre.com/images/illustrations/pyramide_grande_taille.jpg

If I had to guess on the "S" I would say the Syndicat liégeois pour la fabrication des armes de guerre, The Liege Trade Union of Gun makers.

Pete