Here’s a nice little video of a Porsche 904 prototype from 1963/64 – serial number 904-002 – at the Cars and Coffee event in Irvine, California.
Developed as part of the new 100-car-a-year homologation rules introduced in the early 1960s, Ferdinand A. Porsche is down as saying that the 904 was his favourite Porsche design. Though 904s were initially equipped with the 2-litre four cylinder four cam RSK engine to compete in the under two-litre category, it sounds to me like this car now runs a flat six.
We can see that this prototype has some interesting features. The doors finish at the top of the sill lines: other 904s go down into the sills (see the model box pic above). That rear canopy also looks quite flimsy compared to the later 904 held in the Porsche museum (chassis number 008) which seems much less wavy on video.
My guess would be that early cars went as thin as possible, and the engineers added to the thickness of the fibreglass as development continued: something to read up on later. That said, the finished 904 was a light car. Weight was around 650 kilograms, so it could sprint to 60 in six seconds and on to 160 mph.
The blue colour is interesting: a change from the usual silver. I think metallic colours work better on 904s but a prototype is a prototype: if this is how it left the works, you don’t mess with it.