Hard to tell in the video, there looks to be some material missing on the teeth face. Normal wear. You will have a hard time finding a perfect R/P that is 40yrs used. If you are not blasting lots of power through it then it is fine. Gasket tolerance is +/-0.03mm. Consider that is with new bearings in perfect shape. Used bearings are going to have some serious play so close enough is good for the gaskets. Consider that the kits only come with 0.24-25mm gaskets, you get as close as you can with that and roll with it. Sounds crazy, I know. Next question would be, "What if you change to new, tight bearings?" Well, there are other size gaskets that you can order. Also, there are shims under the pinion that you adjust. Now, you can rebuild the box using the standard kit with the 0.25 gaskets, get close enough, and things are all good. How? My only educated guess is that the R/P are worn and the tolerance on them is much looser than new which allows for there to be wider tolerance range. What happens if you are not spot on? Noise. What happens in an old transmission usually? Noise. So, you can be pretty bold in assembly if you just get real close. Thats kind of a gist of the stuff mentioned in the DVD.