I'm guessing that this car is in MOW service and someone neglected to stencil an "X" in front of the number. The numbers are repainted, so this car was definitely renumbered. There is some small slanted white lettering on the distant end of the car that I can't read, possibly denoting it's MOW assignment. The cars in the background all appear to be GN MOW cars. Although many (most) GN MOW cars were completely repainted, many went into MOW service with only new patched numbers.
Do you know the date of the photo?