They were celebrating St Louis first arch
Thanks for posting the photo. It appears to be a modified Model N,R,S, SR Ford. The fenders and running boards for the Model R Runabout and Model S Runabouts were the same parts used on both models. That is the style of running boards and fenders that the car has. Below is a page from the 1908 Ford N,R,S, and S Roadster price list of parts:
But the body appears to be the Model S Roadster – that came with the mother-in-law seat. With the windshield and the resolution of the photo I cannot tell in the Model S Roadster curved metal cowl is or is not still on the body. But you can see the raised section of the body that would keep objects on the floor from just rolling out of the car when you went around corners. The Model N, R, & S Runabout had a flat front floor and you could shoot a marble across the floor mat and it would keep going off the edge and onto the floor. You can also clearly see how the front seat box has the designed in trim etc. that gives room for the rear passenger to enter and sit down on the rear mother-in-law seat. The SR body is very similar to the 1909-10 Model T Mother-in-law roadster bodies.
It could have been put together back in the day from several wrecks (a 1 or 2 year old car is worth rebuilding). It could have been a Model R Runabout owner who wanted the mother-in-law seat (or it may even be a tourabout – it is hard to tell as that area is blocked by the person standing there). And he went to the Ford dealer and ordered the new Model S Roadster body and had it mounted to his Model R (or S) Runabout chassis?
But I do not have any indication that Ford produced the cars with the Roadster body on the R or S chassis (or with the R or S fenders and running boards.
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