We've been through this several times in the past, but the last time was quite some time ago.
This may be slightly different for other nations, it is however how it works in the EU. Unfortuntaley I found out that it works the same from NZ too, when I received a broken Witch-king Crown last year.
Postal insurance:
Once a package is signed for, the postal service will deny any responsibility for damages.
The obvious thing then would be to inspect the contents before signing. Unfortunately, the postman is not allowed to let you do that.
Catch 22 indeed...
So, unless it is obvious from the outside of the package (damaged/ripped/severly beaten/sounds of fractured polystone when you shake the box a bit, etc), there is no way of knowing that the contents are as they should be. Signing for it means that you accept it as it is, releasing the postal service from responsibility.
Now then, should you find the contents FUBAR or at least not as they should be, the only thing you can do is contact the seller, hoping that he'll do something for you. Mind you, he is not obliged to!
So what good is insurance then?
Not a lot IMHO. The only time it can help you, is when the parcel went AWOL. And even then it is not a nice thing to deal with...
For starters, the only one that can try to file a claim is the sender, not the receiver.
Second, you need complete evidence to show that you sent what you claim you sent. That normally includes an original purchase receipt.
Third, honoured claims will only pay out either the amount of the original purchase price OR the maximum possible insurance amount, whichever is lower. In the EU, the max insurance is about E550,- From the EU to the US is probably even lower.
Letter post (for those of you that send autographs and stuff) carries no insurance at all, nor can you purchase it for this.
Fourth, should the postal authorities be aware that it is a collectible or an antique (or something of a similar nature) that you try to claim, then they will in all probability deny the claim in full. It is in their general rules, which of course nobody ever reads.
How do I know all this?
I'm sad to say that it is experience talking here...
From the five claims that I had to make as a seller, only one was honoured. It took close to a year and only paid out E550,- for a missing Cave Troll that had sold for E950,-
So... indeed, I deny all responsibilities once it's dropped off at the PO.
Should a package go walkies, then I will naturally fully co-operate with the buyer to reclaim funds, but I will not be held to pay back money that cannot be retrieved.
BTW before I knew how all this worked, I was scammed out of a mint statue by a dishonest buyer. I refunded the money he had paid me for the statue and got it back in pieces, just like he said he received it.
Postal services denied responsibility, so I was left with a polystone puzzle where I used to have a mint statue.
When I sent it for restoration (much later), it turned out that a piece was missing and there was substantial evidence that it might now be the one I sent in the first place.
So in effect what happend was that the buyer bought a statue he already had, but was broken. He received mine in mint condition, but claimed it was broken in transit and requested a refund. Refund was sent and he returned the broken statue. He now had a perfect item, effectively swapped his old and broken one for it, and it had cost him zilch.
Honesty prevails, but be careful out there.
As they say: "trust in God, but lock your car door"
:win 
