I've given up on guessing about any silver F1. Unless the photo comes with the info of an owner, or chassis number, I really don't think it's possible to guess or use the process of elimination very effectively. Also, depending on lighting and also the camera taking the photo, the same silver color can look very different. If I have the white balance set to indoor -vs- outdoor on my digital, it creates a drastic difference in the colors that come through on the photo.
I didn't know that the car on the track infield was Chamber's F1 (thanks Drew!!) but I have to say that I don't understand why it wears that UK plate. The other photos I have seen of his car don't show it wearing a UK plate or even any front plate that I recall.
I do believe that the black F1 is Selldorff's, but I think that photo was taken at either the ICI who brought it in to the US, or possibly could have come from before the car made it here. Hard to speculate on that though. The fact that the tires are covered in a white powder substance suggest to me that the photo was taken in a bodyshop.
>8^)
ER