Why do such a mod? Well, My friend 7 gor had a 7549-7010 with a dead movement (probably due to bad coil) and he decided to convert it to become a day-date auto tuna. From the case design, we can speculate that the perhaps the original plan is to make one with a automatic movement. However, since the 1979s was the period of the Quartz watches, naturally, the 7549-7010 was fitted with a quartz movement.
The original dial has the word QUARTZ word...as below..
Original Movement for 7549-70107549-7010 case but one must must use back the 7549-7010 stem. It is worth noting that the 7549 case is thicker.
The dial has been changed to one without the word QUARTZ, keeping the Japanese day date movement and date disc, plus fitted with a black PVD case protector and the bezel has also has black PVD coating to give the watch a modern look.
The 7549-7010 has several compatible parts (with the 6309-7040/7290) , which are : bezel insert, caseback, crown (except the stem), gaskets related to the above are also compatible (bezel gasket, crown gasket, caseback gasket). Crystal and crystal gasket are NOT compatible.