If you note the stack design, you'll see this isn't a standard C4-S-1a Mariner. This is one of three built by Bethlehem San Francisco, suspended during construction for possible Navy conversion, and then completed for Pacific Far East Line. Towards the end of their lifespan they were purchased by Waterman Steamship Company and renamed THOMAS LYNCH, LYMAN HALL, and THOMAS JEFFERSON. By the length of the surname, I'd guess this is THOMAS JEFFERSON (IMO 5057967)

The only one of this type, I have seen in my line is "Carter Braxton", maybe on of the letters fits.
Kind regards
Gerolf

That is one of Waterman Steamship Company's Mariner-class cargo ships. However, they operated 6 ships if that type and I cannot say for sure which one that is.

A Mariner-class C4-S-1a like this one:
https://www.shipspotting.com/photos/581168?navList=moreOfThisShip&imo=5158993&lid=159768