All the older ones used the ETA 7750 movement. The only problem with these is that you can't change the date between about 10:00 PM and 2:00 AM.
Its a little hard to explain, but I'll try. During this time there is a wheel that is engaged with the calendar disk. If you try to move the calendar disk to a different date, it gets stuck on the wheel that is trying to turn it. If you force it, you bend the finger on the wheel to a new position and it changes the time that it automatically advances. It happens all the time on this model, but usually doesn't cause other problems.
It is a problem that can easily be corrected when the watch is overhauled, but not corrected easily as a small job.