The bar is the oddest “wheel” that comes with Spirograph sets. This video is just an introduction to it, demonstrating hole 1 in both rings.
With ring 144/96, the bar produces a 12-pointed pattern. With ring 150/105 it makes 21 points. So using the Table of Spirograph Points, we see that it matches wheel 40. However, at it’s largest diameter it’s bigger than wheel 40.
If you’ve been avoiding the bar, I hope this video will encourage you to give it a try.