I picked the wrong time to arrive here. First a muggle couple, then a car, then a family with a dog. I ended up having to wait five minutes until the coast was clear. At least that gave me time to inspect the half-way milestone.
The cache was an easy find - always good to see an ammo can cache. In fact I saw it as soon as I arrived (and I'm amazed that it hasn't been spotted by muggles). So after everybody had gone from view, I was able to open it and sign the log.
I've filled all 366 days of my finds grid so I qualify for this challenge. My stats are publicly viewable but I'll attach a screenshot of them anyway.