Well it is still useful but not to you directly. The distinction being that the right intermediary could make use of it.

If you had a physics model it could describe it perfectly but it would likely involve a very large group of matricies and linear algebra constraints. You technically could work through every equation given a large set but examining the watch yourself would likely be quicker, if not learning to be a sufficiently good watchmaker.

However if you assemble a computer model to handle every component's interaction individuallt and a physics engine to do number crunching you could get a working mathematical model of the clock.