I'm not certain about this one but I'll try O-9-n.
I think Car O is a Hanomag, maybe a 3/16 PS, but I could be wrong. The architecture link would be with 9, the ex-Hanomag factory in Hanover, which I'm sure has appeared here before.
The problem has been finding an extra. I know that Hanomag was progressively taken over by the Japanese Komatsu corporation, who now occupy the Hanover building, but that didn't seem to help until I browsed the "history" section of Komatsu's website. There it says that they produced Japan's first agricultural tractor in 1931, and the picture is Extra n. That surprised me, as I assumed n was a Caterpillar 2-ton crawler - it certainly looks just like one. I haven't found any mention of a licensing agreement, so did they just make a blatant copy of the Caterpillar, like some Japanese camera manufacturers made literal copies of Leica and Rolleiflex models?