Lovely vehicles ! The D3 and D4 where similar to the earlier Chenard & Walcker vans.
Actually - as you may know of course - your drawing shows the minibus variant, while the photograph shows the van or “fourgon" version.
In attachment is a small ( sorry, I don' t have a larger one ) print of the van as seen in your photograph.
Last July, we were travelling through France, where I shot some pictures of these two abandoned specimens ...