http://www.vintagehour.com/rolex-tropic-crystals-a-comparison-of-superdomes-domes-service-domes/

: I've finally got around to having a Superdome crystal fitted to my
: Sub 1680. I know purists might sneer, but I can't tell you what
: a huge difference it makes. The watch is so much more wearable
: now, the dial more legible without the cyclops being in the way.
: The crystal giving the lume plots a beautiful 'oval distortion'.
: The cyclops never really made much sense to me.. it broke up the
: clean dial and you had to look at it dead-on to see the
: magnified date. For a tool dive watch, I always thought this a
: frilly pointless addition. Plus the original 'top-hat' crystal
: was fairly flat, and was very 'mineral glass-like'.. I'm so
: pleased with the super dome.

: Thanks to Jimbo for sorting it all for me!

: Anyway, enough waffling - here it is, a '78 Sub 1680 with Superdome
: crystal..

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: Stewart
: - Heuerville