Nice idea but there are problems. If you look at both movments the hands fit on different size posts (widths) on the movements. you may also need a different movement holder. I did a lot of research on this. I also own a few 7750 and Swiss ETA Clones . I found that the 21J is just as Reliable as the Asian ETA Clone. What you give up is the smoother ticking of the second hands, lack of hacking, and the 21J is not quite as precise as the ETA in accuracty. The 21J DG 2813 is a copy of a Myota 8515 Citizen movement and and has been in use for years Since 1970's. It is sort of like the Seiko Auto movment in my 007 Diver. The Rotor only winds in one direction while the ETA style winds in both directions. I honestly would buy a Quartz movement over any of the Auto movements as I really want a watch that works but looks cool to me. The price difference is also a factor in the SInn watch. For $218 you get the Asian ETA copy (no Swiss real ETA are avaialble or they are used for that price "rebuilt"). For $ 128 the 21J. If both watches are just as reliable I will go for the 21j. I also read that that if you plan on NOT servicing the movement you are better with the 21j . This Sinn has the same parts (saphire crystal, case , strap) on BOTH models. Most often you get the mineral crystal on Quartz and 21 J but not this one. The shipping is the same on both. There are many cheap 21J movments but if you are gettign this DG2813 or better yet the Myota 8515 you are fine in the reliability. If it were a ROLEX cloen I would get the 28 K beat as everyone looks at how smooth the seconds are.
Steve