Serial Number Range (Mark 6): 55xxxxx-59xxxxx
Notes (Mark 6): The Mark 6 was the dial formerly known as “Mark X.” It was previously thought of only as a service dial because it was first noted as such on much earlier matte and gilt GMTs. More recently, several collectors noted how commonly it was seen in the late 1970’s. After multiple original examples without previous servicing were seen, conventional wisdom has evolved to think of it as the last dial variant of the 1675. At this point they are generally considered original to watches with 5.5+ million serial numbers. When found on much earlier watches they are considered early service dials like were likely installed in the 70’s and 80’s. The cut off of 5.5+ million for original dials is a soft one so while I’d expect to see them there they may not necessarily be a service dial if the SN is a bit below (remember, all the SN’s are a guide and guesstimate – anything but absolute!). As always – assess the watch as a whole and buy the seller.
The Mark 6 has the most elongated crown of any matte dial 1675. Compared to the Mark 5, the base of the coronet is much more circular. The serifs of the ‘Rolex’ text are not sharp angles on the L and E but are smoothed curves. The ‘oyster perpetual’ are much closer together than the other dials and lack significant serifs. The lower text is best differentiated by it’s smooth G of GMT (which lacks the extra vertical line on the lower right) and the O of officially, which runs slightly lower than the rest of the SC/OC text.
Notes (Service Dials): There are both early Mark 6 tritium service dials and late service tritium, luminova, and superluminova dials for 1675’s. There are simple tells on these – the later tritium service dial has a much squatter crown with very clean and shallow but domed plots; the luminova and superluminova service dials don’t have tritium lume plots (and the superluminova only has ‘swiss’ at the bottom).
All pictures credit to HQ Milton.