Unique outhouse model

I found a photo of the prototype on Shorpy, an interesting site that posts old photos.  The model was fairly simple.  There is actually a crude interior to this but can only be seen by viewing from above. 

Below is a view with the prototype in the background.

And below is a view of the model from the back.

I have run out of room to install any but the very smallest new structures on my layout.  I may build some replacements for older models that could be better replaced by something newer.  I am now trying to decide what to do next - a continuing problem as I have done so many different things already.