Posted By:
damian
yes, the insurance policy is rather complicated, but i am only a letter carrier and will ask tomorrow in my office.
what i do know is "registered" mail is top dog. If i was to lose one i could be fired automatically. these things are signed over at every location. A postmaster would be in some trouble if someone lost one, not fired i'm sure but no having fun for a bit. they have the truck drivers sign for these as well, they get their own little bags (seperate from normal mail/parcels/priority et al) they have metal serial numbered tags that go over the bags and on trucks locks that have to be verified and changed at every stop. Basically thats armored car worthy to the USPS.
So if you want it the safest route, go Registered and insure it to your hearts content. anything of value to you or the provider should go this way.
P.S. The post office gets a bad rap all the time, but i will say this, UPS, FedEx, DHL, pick you server. they all have their faults also, noones perfect 
and none of them will send a letter from the tip of Florida to the tip of Alaska, forward that to Hawaii, all for 38 cents.
Good Luck!