Last year I bought a new PC, going through my pics I came across some pictures with what appear to be metallic orbs on, I did not see them at the time.
What ever they are they were silent, spherical, and moving far too fast for balloons.
These two pics are cropped from full pictures, that I couldn't down load (too big ?) I will compress the others and put them up. Unfortunately I only had a 7.2 mega pic camera at the time.
I estimate them to be about 2-3 meters across, the mountains behind rise from 300 to 1100 meters (clearer on full pic)