Can't find timing mark on balancer

The outer rim is smooth everywhere with no mark at all?
Hi! I'm new to this forum. I have an E Body, and am a member of the E Body forum.
Now my son has an A Body that I enjoy working with him on.
I can't find a timing mark on the balancer. We know about where it should be, because the car runs and we have rotated the crank and have the the rotor pointed to the #1 cylinder.
72 Dart Swinger, maybe not the original 318.
Does anyone have any input on this?
Timing marks changed from the passenger side to the drivers side in 1970. It’s possible that you have a mismatched front end on your engine. This is pretty common when there has been an engine swap
The outer rim is smooth everywhere with no mark at all?
Yes, the balancer is smooth everywhere with no marks at all. I know how to find TDC and will make a permanant mark on the balancer when I do. I just wanted to know why there is no mark on the balancer.