Laser Etched Crown (LEC) start dates??

[Coolshades]

Can someone please direct me to a reference that shows when Rolex started using laser etched crowns on their different models? I am striking out with Google searches and searches on this form. Specifically did they start on all models in the same year or were they phased in on different models like the maxi dial and solid link bracelets etc.

I am asking because I recently was offered a Daytona by an established pre-owned dealer with a 2008 serial number. It did not have an LEC. There were some smaller issues with the dial that raised my suspicion too so I did not purchase the watch. I purchased a new GMT II from an AD back in 2008 with a 2007 serial number and that watch has the laser etched crown so I thought the Daytona should have it as well.

Also along the same lines does anyone know if you send an older Rolex watch in to the factory service center for crystal replacement, will it come back with an LEC even though it did not have one when it was originally made?

Thanks for the help!