The three posts that Tom refers to can be seen here:
http://www.wooljersey.com/
If you go to the expanded view, you can clearly see the washers in question, but they seen to vary ever so slightly. While they notoriously go missing, I don't really recall getting a new post without one. I'm not entirely sure why they are so important, but they certainly seem to be. Those posts were known for not holding as well as some other posts, and there were a number of "fixes" that evolved, most already mentioned. By the way, I learned much too late that the bolt head is really closer to 1/2" than to 13mm, and a Snap-On six-point 1/2" socket (or equivalent) - and NOT a 13mm open-end wrench - is the thing to use if you want to retard damage to the bolt head.
Wayne Bingham Lovettsville VA
>>>>I've noticed that the washer is consistently absent on the earliest
Nuovo SR posts. The first type had the same finish all the way up the
post and onto the cone shaped transition below the uppermost portion,
which had a sandblasted look. On this version, the lettering was on the
cone-shaped section. The next type was the most common, which has the
polished finish on the main section of the post (which was also where
the lettering appeared), a small lip at the transition, and the
"sandblasted" finish on the cone-shaped and uppermost sections. The
last version was full-polish, right to the top. In addition to the
missing washer, the 1st type had pearly anodizing on the clamp pieces,
and the head of the bolt was a bit taller. The distance across the
flats (nominally 13 mm) also seems to be consistently undersized on the
early posts. Anyway, the "missing" washer was apparently never there on
the 1st gen. The consistency with which I've seen the missing washer on
only that version makes it seem like more than a coincidence.
Tom Dalton<<<<