The 753, 752, and 770 were essentially the same movements except for the number of jewels. The 770 has 22 jewels and was top of the line. The 753 used 19 jewels, with no shock jewels on the balance pivots or cap jewel on the fourth wheel. This made it slightly less expensive to produce. The 752 had 17 jewels, eliminating the cap jewels on the escape wheel. Other than that, most parts interchange. All three are excellent movements but IMHO I consider the 770 to be the finest wristwatch movement they ever made. It's a joy to work on, quite obviously designed with the watchmaker in mind.
If you like movement pictures, here's a pretty special one:
Obviously this is a pocket watch rather than a wristwatch, but it's historic and unique. It's a Hamilton 992 that was made just before WWII, then shelved for the duration. It was brought out after the war and was displayed extensively at jewelers' conventions. It is also featured prominently in the opening title sequences of the 1947 Hamilton factory promotional film "What Makes a Fine Watch Fine" and the 1950 film "How a Watch Works." (Both films can be viewed or downloaded at www.archive.org, or purchased from many eBay sellers.)
The movement has plates and bridges made of Lucite to make it entirely see-through -- the ultimate skeleton watch since the only metal parts are gears and other moving parts. All support pieces are Lucite. And yes, it does run great and keeps time like a fine 992 should!
This is the only actual size watch Hamilton made out of Lucite, and was one-of-a-kind. However they did make a number of oversize (8-10 times actual size) display movements.
The Lucite/quartz crystal make the movement look very "uncomplicated". Seeing the wheels of the drive train, escapement, and mainspring...Skeletons of today, I guess, because of the non-transparent metal bridges, make it hard to separate each part of the watch.
Actually, the Waltham "Stone Mountain" watches are extremely rare but not one of a kind. There were quite a few made and several survive in various sizes. I've only seen one in person, they are stunning. But they are only skeletonized from the back so it's not quite as dramatic as Hamilton's Lucite watch, though definitely exquisite...