From the last post here in 2008:

I also have a model 2854 and the serial number is also 967 !! so much for serial numbers..

During "Japanese Industrial Recovery" after WWII a lot of "copies of things" were made. Several people were arrested, some convicted and did jail time, based on "their gun" being found at a crime scene, before it was discovered that the Japanese had made some 3,500 (IIRC) copies of the M19911A1 handgun, shipped to and sold in the US, all with the same serial number as the one they copied. Markings of the original manufacturer of the one they copied were also copied - identically. (There's a fine line between a "copy" and a "counterfeit?)

While it's unlikely you'll go to jail if someone steals someone else's guitar - maybe, the "lesson" here would be that no matter how confident you are that your item is "completely identifiable in original condition," it's probably a good idea to add a unique and identifiable mark of your own so that you can unambiguously testify as to whether the item is yours and not someone else's "look-alike."

You already, of course, have photos of all your "significant treasures" but the photos should show something unique about each item in order to be very useful.

Serial numbers can be defaced or removed, and new ones can be created if the item is worth the effort. Even the dings in the neck from when you got drunk and fell on the speaker stand, if properly documented, could be the more credible identification, if it comes to needing unambiguous proof, although a unique marking that can be described and be recognized by others is more likely to be helpful.

John