: Mark,

: Great minds think alike ;)
: My first chrono was a Swatch Irony chrono with an aluminum case as
: well and got me interested in other chronos, mainly Heuer.

The Swatch website is ideal for watch historians, I was able to find my chrono from the year on the dial:

http://www.swatch.com/zz_en/watches/finder-detail.sku-YCS4001GC.html

There'd be nothing to research if we had that sort of info on Heuers!

: Another great article as well on the different scales. It makes me
: think of another question that I have in the same area. On many
: of the pre 60s/70s chronos the 30 minute counter/subdial has
: extended hash marks at the 3, 6, and 9 positions. What is the
: idea behind these being highlighted?

I think it's just to make the 5 minute divisions clearer and easier to read at a glance. The 10 minute divisions have numerals and it's easier to read 14 or 16, say, if you have the extended mark to highlight 15. If you didn't have that, you'd be reading back or forward from 10 or 20 - much more awkward.