*grmph* You are right that on very old ones they wrote the letters instead of putting stickers on it. Under my research i only found that they write "CATERPILLAR" and not just CAT.

Anyway, in my opinion that is just the grille and not letters. As you can see on your pictures the letters are smaller. As i said, if you give me a good reliable proof i stand back and say its okay. At this point i cant tell what vehicle it is, but i dont see a Caterpillar there.