it can also be just 2 disc fixed on the wire wheel, have to see it in real for know exactly, for 19 cars the tooling for the wheel will be quite crazy ...
My sister has a Rosengart with exactly that (although on one side only)
https://upload.wikimedia.org/wikipedia/commons/b/b4/Rosengart_LR4_1928.jpg(NB Picture of a similar car, not hers!)
