Jay, how do you know it's in St Louis? This is what I found in googling "W Souter & Co." Long way from St. Louis....
(You have to copy and paste the url. The forum doesn't make it all a link.)
Dick, Found the photo surfing the net and that was what was said about it. Sometimes these old photos are misrepresented by the posters for what ever reason.
I think your research is right on and it's a New Zealand photo not St Louis photo.
The roadster has equal half windshield. Also there is striping on this car and hinges on the left door.
Jay, I wouldn't have looked if it hadn't mentioned St. Louis. The Souter name didn't ring any bells and I was curious to see where the building was and whether it was still there. Then one thing led to another...