If that's the S1, wikipedia says they built just one of them. https://en.wikipedia.org/wiki/Pennsylvania_Railroad_class_S1With experimental "duplex drive" and large diameter drivers, it should have been a powerhouse and fast as hell.
Unfortunately, it was fast as hell, but also too powerful and very slippery.
Also prone to derail on complex trackwork, and a pain to work on.
...but damn pretty.
IIRC they had 50 of them, and it wasn't their weirdest design.