Looks like they used dry transfers on clear decal film, and some of the letters didn't stick.
For those who just can't get their decals straight, check your prototype. A J.B. Hunt container went through Prichard, WV on NS a few days ago with the logo panel badly out line. The left end was at least a foot lower than the right end, like someone just stuck it on without bothering to check the alignment. All the others I saw in that train were straight.