I think the question being asked is:

What is the best restored or survivor Sandman in the world.
Meaning an original Sandman that is classed as the pinnacle. The one everybody aspires to be as good as or wants to own the most. The Sandman that is used as the reference for it's model and can/is being used as a guide for the restoration of others.

Second to that: What books and documentation does it have?

What Blocker says, Suggesting a country wide "Sandman off" is exactly the way to find the best of the best. Not unlike a Sandman National Titles.

I guess the question is raised because it comes across as most Sandman's are bitza's and made up from many, without factory books and documented history.
That's not to say they are not Genuine Sandman's but most are far from "original".