I keep mine in a safe at a friends company (they are staffed 24/7). I would not use a safe deposit box because they have been raided over the years (google it). Your best bet is a small fireproof safe that is well hidden at your house or at a family members. I sort of do the same thing for my offline coins...I can not access them without driving to multiple locations.
Like multi-sig but for physical items. Nice, and congratulations on the copper thing.
Yup.. 2 of 3 keys for them.
Not at that point yet, but I always figured rebar through a safe bottom cemented directly into a sub basement should work, no?
They sell safe anchoring kits. You just drill the concrete and use the self expanding bolts to secure it.