Wow - what a pretty puzzle! My favourite so far.
It really is a perfect puzzle: it looks impossible but just needs a couple of insights. I found it without using a GPS (am I the FTFWUAG?) Once I got to the location it took less than 5 minutes to find.
I left a Polish coin in the micro inside the cache. I made sure that I screwed its top back on tight. Its still quite damp inside, and I think that some people before may have put the lid on upside down. I nearly did this myself as I was thinking it was a snap-top.