Caution:
Scott 447 may be trimmed from a Scott 428 to appear to be a perf 10 coil. This alteration is especially appealing on the
used perf 10 stamps which are quite common compared to the used coil stamp. Any used Scott
447 with small margins both top and bottom should be viewed with
suspicion. Another good rule of thumb is that flat plate vertical coil
stamps usually measure about 25 mm in height, that being the height of the
actual stamp, not the design. If the stamp is less than 24.5 mm in height
there is a good chance the used stamp is a trimmed 428.