On modern watches they are found at the 6 o'clock except on the green crystal Milgauss I believe. That "S" on the crown in the picture would suggest its a service crystal with the crystal originally fitted to the watch will not bear that.
nope...never seen it in all the years we have played with and collected vintage Rolexes. also...bear in mind there were a lot of modern Rolexes that didn't have the laser etched crown on their crystals even tho most in the same year ranges did.