I will say this about loss and payment being one whom worked on the inside as a USPS employee for 23 years, what you insure for and what they pay can be two very different stories.
Filing a claim for a 10k watch loss will find you proving value and especially with vintage watches that can be a grey area. What you claim as NOS suddenly gets determined not by you and your experts but theirs! Sit and read the small print sometime!! Regardless the carrier. And I promise, it will be lower than your figure if you can't convince them you are righter than they are. It really is a racket.
As an insider, I only ship one way unless a client asks me to ship another and that is by US registered mail. The only service where if it is lost, someone losses a job! They tend NOT to loss these!! Signed for the entire way, locked in secure bags, hand carried by drivers then hand signed for and scanned at each transfer, locked in safes overnight, can tell you the name of the last person to touch it... I can go on. And when you are dealing with a foreign country some of them I do not ship to at all. There is an old saying in the PO, Italian mailmen all wear Rolexes and they didn't buy them either.
Insurance when shipping is just like life insurance, it is piece of mind if something happens. Basically, you are betting the shipper is going to loss it and they are betting they won't. They rarely do and profit is 100% as they really only need provide a service IF they have to pay a claim..... You have a better chance of your new credit card being lost or stolen than an item you ship if done properly.
Wayne