Seaboards E-class engines were spread out over 4-4-0, 4-6-0, and 2-6-0 locos. I'm beginning to think that drawing is not of a SAL engine. But between it and the photos I have of the real ones I think I can make a go of it.
For SAL engines, the "S" usually designated "Super-Heated". Could be different RRs used letter designations to mean different things?