[springer]

Information in this thread and the time frame that particular dials were used by Rolex based on serial numbers is not science and a "guestimate" based on various dials found on 1675 GMT's compared to their serial numbers. No one can say for sure when dials were discontinued and replaced by other variations or what era the serial numbers should be for a particular dial. You can not say for sure that i.e., Mark 1 dials ended during a certain serial number sequence and another variation of dial was then used by Rolex. While Mark 1 dials replaced the gilt dials after the mid-1960's, the next variation of GMT dials started to appear after the supply of the Mark 1 dials dried up. No one knows when this occurred, as these were just dials to Rolex to market and sell GMT's. You can not say that Mark 1 dials ended around the 21XXXXX serial number and was replaced with the Mark 2. It would be more responsible to say circa 1970 or 1971, as Mark 1 dials were definitely being used by Rolex after serial numbers beginning with 21XXXXX which is circa 1967/68 according to some of the sources that identify serial numbers with production dates.

As an example, I own two 1675 GMT's with 18XXXXX serial numbers (circa 1966) and both have case backs stamped 1st quarter of 1968. The point being that while the serial numbers would indicate much earlier production, the case backs do not. The same logic would apply to dials - except that dials are not dated to verify their era of production.

Also, I would like to emphasize again that the elongated dials were used during the later part of the 1970's on GMT's and are not replacement dials. I believe these were identified as Mark X dials by Orchi.