This view shows the same two insulators from the side, trying to show the mold lines. Viewing the original may help view the detail. The arrow points to the circumferential mold line on the [020]. The usual vertical mold line should be visible on both, and may be seen extending up onto the base of each example. The [017] on the right has a smooth transition from skirt to base, and no circumferential mold line (thus, RB).