The left perfs look wide because the are cut all the way down. The arc cut is typical of coils applied by an affixer, discussed in several previous threads.
To revisit an earlier question in this thread about catalog renumbering:
Short answer: Yes. There has been, so anything labeled as "491" in the past should be reexamined - including this stamp
1927 Scott worldwide catalog showing only 1 type:
I don't have a 1928 catalog, but skipping forward to the 1929 Scott worldwide catalog with types III and II listed, in that order:
Things remain static through at least the 1956 U.S. Specialized catalog with type III being the major type and type II being the "a" subtype:
I don't have 1957 or 1958 catalogs, but by the 1959 U.S. Specialized catalog (scanned here) the 491 listing is split into 491 and 492 as it remains today: