How can you tell if a small block flywheel is neutral or external balanced

By the casting ##?? or reference pics..

External have great big holes, 360 have three of them(2 inch diamterter and around 3/4 inch deep, if I'm remebering correctly) side by side on the outer edge of the flywheel on the starter side . Same thing on the 1972 and 1973 340 but smaller and maybe a little bit different location in relation to TDC on #1, maybe not

The cast crank 340 only had a single balance hole and it's small enough to get confused with the typical mass balance holes unless you know the exact location.