Here's a link to a previous Forum thread on milk cars. According to a post on that thread, the butterdish cars were actually reskinned Pfaudler-type milk tankers, which originally looked like ordinary 40' reefers. That would explain why they do not look like any 1930's flat car I've ever seen. The side rails are different.
And here's a shot of a very similar car belonging to Hood's. You'll have to follow this link; it's the cover shot of a PDF so I couldn't grab it as a JPEG.
