first watch you show in the goldtone version. I remember that I got it shortly after I joined the "old" TWF years ago and had to do a balance wheel replacement to get it running. It was a real "challenge" installing the new balance wheel because I had a lot of trouble attaching the end of the hair spring to the balance coq.
That end of the hair spring is held in a hole in the coq by a tiny brass peg (!) and I had to make a special tool (just a toothpick with sticky tape on one end) to hold it while I then inserted its small tapered end into the hole in which the end of the hair spring had already been inserted. Once that was done, I used the other end of the tool to push the peg securely into place. That watch undoubtedly has one of the weirdest ways of securing the hair spring I've ever seen on a watch, but I guess they went with that design to keep costs down.
Speaking of 21 jewel automatics, I'm happy to report that my Invicta "Pro Diver" is now running normally again. Did I do a formal and elaborate cleaning and relubing of the movement? Nope...I just kept shaking it everytime it stopped and that action, apparently, helped dislodge whatever bit of grit was jamming up the gear train. Hopefully, it landed somewhere so that it wil cause no further problems. At a minimum, a NEW movement should last, IMO, at least 5 years before it needs "routine" servicing...not just the 3 years that I've owned this watch so far.
It's really amazing how VERY sensitive a mechanical watch movement is, especially at the low torque end of its gear train, to the slightest bit of impedance to its normal motion. A single bit of lint or grit in the wrong place can render the most expensive mechanical movement completely useless. For this reason, it is vital that an amateur watchmaker be as careful as possible not to allow any dust to enter a movement while he works on it. If a movement must remain out of the case and exposed to the air for a prolonged period of time, then it should be covered with something, perhaps a large plastic bowl, to keep dust in the air from settling on and sticking to its surfaces. Needless to say, any surface one works on should also be a lint free as possible.