Hey Joe,
The white stuff is fall out ash from Mt. St. Helens, It goes away when the wind blows, and we are lucky that the wind blows a lot here.
Hey Keith,
Funny you should mention that. We had the ambulance down to Fort Douglas last October, the director of the museum told me that the ambulance should not be outside, it should be protected by a building, as he looked at the new addition to the museum. I replied "why? if it gets damaged, I can always make another!"
In 2010, an ambulance like mine sold at auction for over 40 thousand dollars, and the only difference was that it was well weathered, so I figure that any weathering to mine just increases the value.
Best
Gus