Originally Posted by
kevin c
Are those full "sheets" like a full page, made of a single piece of metal?
Linotype ("Lines O' Type") is a thin strip of alloy with a single line of reversed print on one edge. Monotype ("Mono" as in a single letter) is a single reversed letter on a small block of metal, as is foundry type. Lino, mono and foundry alloys are hard, being high in tin and antimony, and higher going from Lino up to foundry.
A full page of reversed print cast in one piece sounds like stereotype. Wikipedia describes stereotype alloy as being between Lino and mono in both tin and antimony content (though there were several proprietary formulas of each, and type casters would occasionally use alloy that was in some degree depleted in tin or antimony, so overlap in content from one type to the next is possible.
Short version is that it is probably a high tin, high antimony alloy. Hardness testing would give you an idea of what it could be used for as is, or, if harder than needed, how much soft lead to mix in to get in the desired range.