Another philatelic use of the Special Delivery envelop:

It was delivered (flown, I presume) to KC and has two KC backstamps. No additional postage was required as the airmail and special delivery rates were covered by the full pane required by the POD. While collectors treated this as an FDC, the cancel does not say "First Day Cover" because the POD considered this a reissue of the 1941 6 cent Transport airmail stamp (C25). But the hand cancel is unique for this issue, as FDC's with just a single stamp will have a normal machine cancel.
Do we know who created/designed this border?