I'm Thinking Of Getting A Fireproof Safe For My Coins, But..

As to moisture, everything above is correct but also: open it now and then!

The biggest deterrent to the casual thief is weight - they probably aren't going to try to force open your safe there, but if they can easily carry it away, they probably will. So if it weighs under 400 lbs and you don't have it full, fill it up with metal so that it is as heavy as you can get it. Obviously there really is no absolutely safe weight - two men and a fork truck can move an amazing amount - but the heavier, the better. It's a curve that works in your favor for every added pound.

Or they rip the bolts right out..

But yes, any obstacle buys time and passing time makes them nervous.

I leave a big jar of change in plain site. It probably comes to less than $100 but it looks impressive and of course if this really was a snatch and bolt, it's somewhat heavy and cumbersome, making it harder to carry more of other things. Cash is very attractive because it doesn't need to be fenced. It might not work, but it's worth leaving out, I think.