The Steel Joist Institute says for Chord Size "1", the top chords were commonly 3/4 x 3/4 x 1/8 or 1 x 1 x 1/8 angles and the bottom chord was the same or 3/8 round bars. They say however that other sizes might have been used and were perfectly adequate.
I got this from the SJI publication "Steel Joist Institute 60-year Manual"