During the hubbing process when creating dies, the single squeeze die may have been started and backed off and the die turned a little. Leaving a partial impression of the columns on the center of the die. After hubbing again or in some cases the hub snaps back into the correct position the extra hubbimg marks show on the center bay # 7 on the memorial reverse. The other bays are cancelled out as the planchet flows into the hub. Because this isn't noticed, these extra bars, the dies get used. Some bars are very minor, some run the length of the bay. On the angled ones the reason they don't get removed is that the deeper indentations from the first hubbings don't get removed because the field/bay is shallow. So they remain and they appear in that location.