How do you distinguish a business strike IHC from proof? Are the die details the same except for polishing, multiple strikes, etc.?
LoL. I would simply presume it must have been a proof coin because of the condition. I have about 80 IH pennies. I am fairly sure all of them were business class because none of them are over G4 (and some are even lower but with a magnifier the date is still there).. In short if you get one in MS, I would presume either someone put it in a sock the day they got it from the bank (as my father began doing in 1913, and gosh I wish I still had that sock) or it was purchased by a collector and passed down as a protected collectible from generation to generation, and it was probably a proof coin when it was acquired. I guess the holy grail would be to find one in the original mint packaging of the 1870s, 1880s, 1890s or 1900s. Perhaps with the purchase invoice describing the coin.. Hey good luck with that...
Dentils and rims are more square - besides the mirror fields. Some reading for you leisure - http://www.indianheads.org/CollectionProofs.html. . You can probably find more information on Rick Snows website.