Is there something about that model that is obsure and sets it aside from other machines?

Sewing machines do not have timing belts. They have belts that run from the motor shaft and around the wheel.

Changing the belt on most machines is usually a relatively simple and straightforward process just as changing the same type of belt on a vacuum cleaner is. There is no calibration to a sewing machine belt as there is on a car engine.

The touch and sew has a bad reputation. That is about the time that Singer took a deep nosedive and people threatened to throw their machines out the window.

Perhaps you are referring to an internal belt. It turns a timed and calibrated part of the machine but the belt , itself, doesn't require any calibration. Timing on a sewing machine has different logistics.

Give it a google and I will bet that you can find what you need to know.

Are you having problems with your machine that you are trying to fix?

Remember that google is your friend.