This is a wheel thrown pottery mug.
It's finished in a variety of brown and blue hues.
It features a wide vertically ribbed handle with a thumb rest on the top.
On the front is an image of a train with "GRAND CANYON" printed above it and "RAILWAY" printed beneath it. Under "RAILWAY" in a small font is printed "SINCE 1901."
This mug is signed on its bottom surface though I can't quite read what it says. I also believe it says "03" indicating it was made in 2003.
Condition note: there is a hint of wear on the bottom rim. Please see the last photo for a look at this.