It's hard to make the masking tape cross over the transition horizontally then make the quick transition to vertical, but it appears that's what they did at the time.

All, just thought I'd post a few followup pictures in case anyone is wondering in the future.

I found an old tank that someone had spray painted over. However, you could still see the old stripe through the new paint. I traced it in masking tape so it would show up in pictures.

Correct...