440 distributor indexing

If you still have your factory original distributor in your 440 can you see a line scribed on the base of dist that lines up with a tiny groove in the block when timing is close to the factory spec? Did the production line use this or an actual timing light?

Production did that.

I do something similar after mine is all together and timed at 36 total mechanical (vacuum disconnected).

I use a magic marker and mark the distributor base and block so I can tell at a glance if it's off.

Didn't know the factory did it. That's pretty cool!