Sadly, it's entirely metal, the entire thing is metal with a thick coat of paint (probably why it could be mistaken for plastic) Even the flap is alu.
I've also been considering the repeater method, but sadly, short of parking my bike in the outdoor bike area across from the mailboxes, and leaving a repeater on the back of my bike, I have nowhere to put a repeater, and I prefer to keep my bike in the cellar.
Another sad thing. I started putting together a BOM, and now my biggest problem isn't getting the signal out of the metal box, but to afford the whole thing :/ I'd need 2 moteinos minimum, preferably a third for OTA programming, an indoor display, which would double as my watch (I've been looking at 64x32 RGB LED displays, as the are the cheapest large scale matrix displays I can find) and when I add all this up, it gets to around 150$ which I can't afford :/
So, until I get myself a better source of income, I guess this project will have to stay in my "todo" folder :/
That said, when the time does come, I really liked the idea of popping open the lid now and then to transmit!
Kinda like a little creature popping out to shout it's most recent findings