Whether a watch has papers or not is no reliable indication of provenance.
The important thing is how well you know the seller and if he can honestly tell you the provenance of the watch.
If the watch has passed through multiple hands, it is still possible that the chain of custody was broken at some point and the subsequent owners might not know, honestly.
"A Purist does not believe in gilt by association. Respect, AND disdain, have to be earned..."