1932 serial number starts with D5

[evobuilder]

I just bought a very hot rodded 32 Roadster with a serial that starts with "D5". The frame does not look like a standard 32 (see my other thread where I realized I have something different).

So.... now I am being told the "D" frames are super rare (too late, this one has been boxed and modded), but I am trying to understand the D frames over the 18- frames.

I did search, I did hunt, and I found a ton of information, but noting related to the "D" serial number.

This is my first 32, so I have a lot to learn, but the "D" is throwing me.