I have been following this discussion with interest, as I have
recently been involved with the excavatiion and survey of a number of
early historic ironmaking sites in the north of England.  Sheffield
in the eighteenth and nineteenth centuries gained a reputation for
the production of high-grade steel; part of this was due to the
processes involved )which were developed locally), but a significant
factor was the steelmakers' insistence on the use of best quality
Swedish iron (cast iron smelted in charcoal-fired blast furnaces).

The iron was always stamped with the mark of the furnace or forge
from which it originated, and the surviving records of many of the
old Sheffield firms are full of references to these patterns and
marks.  A good summary of the iron marking situation with regard to
steelmaking is found in Barraclough's seminal work "Steelmaking
Before Bessemer" (2 vols) 1984, published by the Metals Society,
London.  Now out of print but most libraries should have a copy.

If anyone requires more detailed or specific information I have
access to a number of sources for this.

Paul Belford
ARCUS
Research School of Archaeology
University of Sheffield
Sheffield
England
Paul Belford
ARCUS
University of Sheffield
UK