Maybe someone has the right information on here -- my curiosity has
me wondering about a marking cast into the bottom section of a piano
harp plate on a Stroud upright. The mark is a "SF" inside a diamond.

The top right of the plate has the typical builder name cast into
the plate: "Manufactured by The Aeolian Company..." I would have
thought that Aeolian was more or less a large, vertically integrated
organisation that cast it's own plates, given their size and output.

I surmise that the mark at the bottom of the plate was a mark of
Superior Foundry of Ohio based on old trade magazine advertisements.
The ads show a similar diamond as Superior's logo. I wonder how many
piano builder's used Superior's plates? Was Superior in fact owned by
Aeolian? Perhaps I'm mistaken but what would the "SF" mark represent
otherwise? What other pianos have this mark among Aeolian's Stroud,
Steck, Weber line?

The Fairbanks Company was another major piano plate foundry based in
Ohio, but that's another discussion.

David Tymoshchuk