As you know, a 3d object is represented with x y z to define it’s shape and form while the skin that is wrapped around the modell is only in 2d, x and y. The modelling program needs a way to use this 2d texture to actually be able to wrap it around the modell and that’s what the uvw map does.
Here’s what I did to flip that map:
First I imported the modell, then selected the triangles that has the signs.

Then I applied a material temporarly so I could see how it looked.

Notice that the image on the right is flipped compared to the left one. I then opened the modifier list and selected the “unwrap uvw” modifier.

Went down to the parameters group and pressed the edit button. The window to the left shows how the uv looks like for the signs. There’s two groups with 2 triangles each on top of each other, one for each sign.

Those need to be separeted so one of them can be flipped and this is done by selecting the vertices in each corner and using the move tool.

As you can see on the model in the background, when I moved the first group to left and down, the “sign” didn’t change on the right side of the commandpost, so I had obviously moved the left part. Now, I selected the other part and used the mirror tool. Observe the model in the background is now correct.

Last I moved the left part back on top of the right part and then closed the window

After that I removed the material I had used and then exported the model again, and that’s it.