The watch pictured here is officially a référence 6694 (correctly engraved at 12’) with serial 12694XX (correctly engraved at 6’) so a watch produced in 1965. In summary a regular Oyster Date Précision non chronometer.
As one can notice the dial mentions Rolex Royal so de facto that Oyster should be a reference 6426 (because of the smooth bezel) and not 6694. But that watch has in fact 3 different references all engraved/stamped by Rolex.
Now if we refer to the caseback the watch was born 6427 (engine turned bezel) and is stamped date II.61 but to that référence had been added ref 6426 for smooth bezel.
So to sum up we have a 1965 cased 6694 with a back case stamped 6427 / 1961 then engraved 6426 because it lost its engine turned bezel for a smooth one.
Now (if you still follow) a 6694 should have the 1215 or the later 1225 calibre both with center second and cyclop date feature but that particular watch has been transformed to receive the 1210 which is correct with reference 6427/6426.
So that 6694/6427/6426 has a small second hands at 6 and no central seconds as it should normally have on an Oyster Précision date 6694.
But let switch to the weirdest part. To that no date caliber (1210) someone decided to add a date device and went to the trouble to modify the caliber and added a long crescent hand like on tri compax watches and a printed chemin de fer on the dial starting to 1 and ending to 31.
In the auction room were all the usual people (collectors/dealers) telling the watch was an obvious fake but still the watch was wellfought.
To make it short and avoid you to take another Tylenol, I bought the watch and went to see my regular watch maker that dismantled the watch and told me the job has been done properly and told me he was quite impressed with how the date device had been added because the crescent fitted very precisely the date indicator on the external part of the dial exactly at 12' with a nice click sound.
I then took the watch to Paris RSC to have their opinion and they told me that as the watch has various references (respectfully added to each evolution) someone took the trouble and the time to transform the 6427 ref to a more correct ref 6426 (because of the smooth bezel), the quality redone dial swiss signed with a chemin de fer starting from 1 to 31, the Rolex service marks, the précision and the clear click when date is changing, and other details they told me that work must have been done someone from the house meaning a Rolex watchmaker made all these changes a long long time ago.
Now one can ask for what purpose ? A customer order ? Just the pleasure of the challenge ? A school work a bit in the idea of the moonphase created by Franck Muller at L’Ecole D’Horlogerie de Genève from a simple SS Oyster Perpetual ?
I love that completely illogical watch which remains a fun mystery and the most franken and puzzling piece I ever met in my collector’s life. 😊