There are so many different ways to set up a watch depending on its intended functions that it is often hard to give a definitive answer to a question such as: how many gear trains does a movement have?
Unfortunately, it isn’t acceptable to shrug and mutter some lame excuse about why it is so difficult to say, when asked this question, so you need an answer that is serviceable and explicable at least.
It isn’t like someone with a gun to your head has a golden envelope containing the definitive answer, and is insisting your answer matches theirs. If you can answer confidently and justify your reasoning, no one in their right mind will blow your brains out.
However, if you ever find yourself in the above situation, you probably aren’t dealing with someone in their right mind…
Here we go: a simple movement has FIVE gear trains and they are:
THE MOTION WORK is a 12/1 reduction train responsible for moving the hands (not to be confused with the hand setting train, which drives the motion work). The motion work consists of the cannon pinion, minute wheel and hour wheel.
THE WINDING TRAIN consists of the crown, stem, winding pinion, crown wheel (any additional parts such as the intermediate or auxiliary wheels) the ratchet wheel and the barrel arbour.
THE HAND SETTING TRAIN is the keyless work (see older post To Key or not to Key), when the crown is moved into the setting position (usually the furthest it can be pulled out). The Hand Setting Train engages with the motion work by way of the intermediate wheel.
THE TIME TRAIN consists of the barrel and centre wheel pinion.
THE COUNTING TRAIN consists of the centre wheel, third wheel pinion, third wheel, fourth wheel pinion, fourth wheel and the escape wheel pinion.
Now, it is acceptable to roll the counting train and time train together under the heading The Going Train. Dropping your answer from 5 to 4 is justifiable, but it is preferable to show your awareness of the possible division of the going train.
Just to clarify, THE GOING TRAIN thus consists of: the barrel, centre wheel pinion, centre wheel, third wheel pinion, third wheel, fourth wheel pinion, fourth wheel and the escape wheel pinion.
I hope that helped clear up this issue.