I don't have a dial back timing light, but i did get one of these
https://www.summitracing.com/parts/s...BoChAAQAvD_BwE from my local parts store and used it with my regular timing light along with my tach to view when and how much initial, mechanical and vacum advance my distributor was putting out. It worked great and I picked up a few stray ponies by getting it all dialed in.