I have a passenger set with a #38 loco, “Mfg. Co”, vents in end doors, pedestal headlight... c. 1916-17.
Maroon with gold window trim.
The passenger set was Catalog Outfit #40, and included (2) #35 Pullman coaches, and (1) #36 Observation car. My cars are also maroon, to match the loco.
There was also a cataloged freight set with a #38 loco. I would have to look up the specific cars.
I do not know if the black loco suggests that would have belonged with a freight set... I am not aware of 30-series passenger coaches in black.
Your "new" 38 is very nice, by the way!