I knew it was from the 150-car option order. GE was the builder of record, with assembly at Erie, car shells built at the Red Lion assembly plant.
GE assembled and delivered many at MU units at Erie, but later orders the stainless car shells were built under subcontract by AVCO (Nashville) and Canadian Vickers (Montreal), under Budd license. This included the M-2 Cosmopolitans (base order 1972-74, option order 1975-76), Silverliner IV (1973-76), Arrow II (1974) and Arrow III (1977-78). The last few leftover Arrow III car shells ended up going to Metro-North as the West-of-Hudson (Port Jervis) Comet I-A coaches in 1978.
For comparison, here's a
GE builder plate from a MNCR M-2 Cosmopolitan. No Budd mention, as the car body was supplied from Nashville or Montreal as noted above.
I have yet to see an original Silverliner IV GE builder plate, not sure if any remain.
Since my friend continues to chain smoke nonstop, she is probably an Alco.