On the "Locomotives and rolling stock: general discussion" forum a question was asked about the "first all-steel passenger railcar," which may have been (on some decision about what does and doesn't count) IRT 3342 of 1904. I've posted what I could find in two books there: I'm sure there are regulars on this forum who know LOTS more than I do, so feel free to check what I've said and contribute!
Railroad Forums
String on early IRT cars
- Discussion relating to the past and present operations of the NYC Subway, PATH, and Staten Island Railway (SIRT).
Moderator: GirlOnTheTrain
Gene Samsone of NYCT (who authors the "New York Subways 1867-" series books about all subway and el equipment) notes that at the time the IRT was planning its first cars, the only all-steel cars were experimental coaches built by PRR's Altoona shops. These would likely be the first steel cars.
Since my friend continues to chain smoke nonstop, she is probably an Alco.
IRT 3344 has survived, but in need of a lot of work at Branford, CT