I'd guess early Mavic headset, but not prototype. I say this because I have one just like it still in its Mavic box, and there were a couple of more just like it at the store I got it from back in the late 1970s (Marina del Rey bike shop here in Southern California).
The lack of steel races looked like too much hubris on the part of Mavic (from JPR design?) and soon after (?) they incorporated steel races into the headset. Sometimes lightness isn't the King but turns out to be only the Joker.
Chuck Schmidt South Pasadena, CA
On May 1, 2007, at 10:00 AM, Bingham, Wayne wrote:
> Tom -
>
> I've never seen a Mavic SSC headset that looked quite like that one
> either. I'm staring at a Mavic SSC top-nut (the only piece I have
> left
> from this particular headset) and while it looks similar, it is
> different in several ways. The one I have is keyed for the same tool,
> but the bevel at the top is much shallower, and the lip above the
> bevel
> is wider and printed with "Mavic" and "SSC" opposite each other. On
> mine, the faces between the slots have a very slight facet, rather
> than
> being straight (as on the eBay version). Mine has a very distinct
> internal shoulder below the top lip that creates a groove for an o-
> ring.
> On the eBay version, there may be a groove above the thread-line that
> holds an o-ring, but on mine there is much more of a space between the
> thread-line and the o-ring lip, which is very pronounced and obvious.
> And mine is anodized, of course.
>
> I would tend to support your "prototype" theory. Interesting.
>
> Wayne Bingham
> Lovettsville VA USA
>
>
>>>>
> There is a French threaded Mavic headset up on Ebay, ending soon. It
> looks quite different from the examples sof this style of Mavic
> headset
> that I have seen previously. Apparently, it is all alloy, with no
> pressed in steel race inserts. How could this possibly last?
> Might it
> be a "for show only" prototype cranked out for a bike show, before
> production was really begun? It also seems to be unused, but quite
> corroded, which suggests that it may not have been anodized. All the
> examples I've seen were very nicely anodized. In fact, almost every
> Mavic part I can recall seeing was anodized, other than a few hubs.
> The lack of anodizing makes me wonder if it was not regular
> production.
> Finally, I'll speculate that if Mavic were going to do a pre-
> production
> prototype, it would be in the domestic thread spec.
>
> http://ebay.com/
>
> 140111336812
>
> Tom Dalton