Signature Confirm adds a layer of security, but it's not the end-all. You can beef up Signature Confirm service, as well. You can request that someone over 18 must sign and you can even require that the actual recipient you've addressed your parcel to must be the person to sign. Of course they have to show photo ID and it's more costlier. I think it's called "Restricted Delivery." I've used it once.
Registered Mail is the most secure, it's also the slowest...and last time I used it there were special wrapping requirements, such as using that brown tape that has to be moistened before being applied, etc. That's the one where everyone that handles the parcel has to sign off and make a paper trail. Pretty secure but Pretty costly, too. But if something does go wrong you're still left with dealing with Uncle Sam to collect.
USPS Insurance is not worth a dime. Don't pay for extra. It is near impossible to collect. Good advice about that was already given ^^^.
The best "insurance" offered thru USPS is the security of their delivery system itself. If, by chance, you have solid employees at your regional hub, a competent crew at your local PO and a good route man, then you're golden 95% of the time.

Most of my packages route in/out of the Nashville USPS hub. I've never had an issue when that's the shipping route for me.
OTOH, I've had 2 padded envelopes of blades shipped to me, that went thru Memphis arrive with razor clean box cutter slits on the corners and contents emptied out. I'd be willing to bet it was an inside job, maybe even the same worker. Just a hunch.
This brings me to the most important secure shipping method that
you're in control of >>>
how your parcel is packed. Use boxes, never envelopes. Seal your blade in a box inside of the actual shipping box. Pack in a lot of messy styro peanuts. Tape all seams-- ALL SEAMS. Tape your item to the inside of the the outer box. Use a novelty tape on the outside of the clear packing tape. These things will deter some unscrupulous USPS workers from "damaging" the box and going over your ordinary clear packing tape with their own. They're like the rest of us, time crunched on the line and they don't have time to clean up messes and have special tape on hand to clean up the trail of their misdeeds. So they often will pass over things that look like too much risk/reward potential that will bring suspicion upon them. Basically make it as difficult and messy for any thief-- gov't. paid, or otherwise-- to get your blade out of the box as possible. The other side of the coin is, it makes it more worrysome for your legit buyer to get their fix, but most of the time, Busse buyers are smart enough to realize when they have to take a Jackhammer <see what I done there?


> to their parcels, they know it for what it is and are most appreciative of the extra security measure. Even if it means delayed gratification for a couple extra min.
If you sell a lot and ship a lot get a third party shipping insurer. They pay off with a minimum of headaches if you have a claim. Of course, you're still out your merch. but you at least get some sort of compensation. With USPS you're gonna lose your blade and not collect a dime compensation.


Sorry it's so long, but I wanna help my Busse bros to have success in securing their goods safely!
In closing there's no such thing as a "sure thing" when it comes to shipping a fine blade regardless of shipper, but USPS gets the job done very well for me almost every time...It was a different era, but this is still a remarkable story some of you may have not read about yet, ENJOY!
https://postalmuseumblog.si.edu/2012/11/delivering-the-hope-diamond.html