I've looked at the images for a while. The only thing I see is that the width of the 1 colon, including perforations, seems to be wider than the 40 or 50 centimos. From a cursory measurement, the images themselves seem to be the same. However, I cannot be 100% sure from the scan.
I purchased this piece about 40 years ago. The stamps are overprinted in the wrong colors. The note that came with the set stated that only one sheet of each were printed (to knowledge of the time) and that only a handful were known on cover or piece.