This may explain it as in the late 1870s Belgium purchased some of the Steinhauser Works of Witten infrastructure: http://books.google.com/books?id=5XGBAAA...ny&f=false, ; therefore, Sl(Syndicat Liegeois), could still apply to the "Sl" stamp.

Anyone confirm that Witten Excelsior steel came from Witten or Essen?

Kind Regards,
Raimey
rse