wondering about earliest use of aluminum double-hung windows...  We have
1930s limestone 8-story tower here in A2, MI.  Currently windows are
aluminum, old, but are they original?  Drawings show a different
configuration, probably steel, but with the troubling note to see a
revised detail sheet, which, of course, is missing.  My thinking is they
were replaced in the early 1960s, but can't confirm.  Owner wants to
replace them now anyway with something more energy-efficient.  That
might be acceptable, as long as we are assured that they are not
original to the building.

Ilene