This flap is the same as the F-1a in all aspects except the "tabs" that connect the lettering to the border. These tabs cause this flap to be referred to as the "chain stitch" flap. This is the most rare of the older Chicksa 202 flaps. It is estimated that a mint condition copy of this flap has sold for from $300 to $500 by 5/97. I have been told that the F-1c was issued before the F-1b and that this flap was issued in the mid 1960's.