This is a replacement belt for the pitch control / speed adjustment for Dual 505 turntables. The same belt is used on models 1, 2, 3 and 4. It needs to be printed with TPU, as it has to be flexible.
The original belt uses a custom tooth profile, but it's not a high torque belt, so an exact tooth profile fit isn't needed. This model uses GT2 profile, which works fine.

I've included two versions of the belt model with slightly different radiuses, for a tighter or looser fit. The best one to use will depend on the shore hardness of your TPU filament. The 21.9mm version worked for me with 85A shore hardness filament. If your belt doesn't stretch enough, try the 22.2mm version. I removed the metal grip washer, and black plastic washer on the control knob shaft to fit the belt without extra stretching.

If you need to modify it, I've included the Fusion file, which uses the GT2 timing belt generator by @JohnCTOofRackRobotic - https://www.printables.com/model/606343-perfect-belt-generator-gt2-timing-belts
You can change the parameters in Fusion to tweak the number of teeth used in the model. 21.9 = 74 teeth. 22.2mm = 75 teeth.