I thought that there were only two cars built for the 1914 French Grand Prix, but you are right, this is claimed to be one of them, rebodied after WW1. I think this is quite plausible, as I have found two sources which talk of one of the GP cars being rebodied for road use.
I'll post a couple of pictures tomorrow when I can get to my other machine, but in the meantime, if anyone has anything else, we'd be glad to see it.