View down into the hole for the right-hand headlight bucket
Since I had the headlight buckets out I figured it would be a good time to inspect the inside of the front of the fenders. And, low and behold, found a cavity that was full of sand and gravel - and clearly had been wet in the past. The first three photo's in this gallery show where the cavity is, and give some idea of how much crud had accumulated.
The bit of leather on the upper lip is what I use to hold the head-light bucket in place while I tighten the nuts that mount it to the bracket. You can see the rusty pocket just below the bracket.