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One major difference that can make identifying principal between Topps and O-Pee-Chee unmistakable may be the language on the back from the card. The informative blurb on Topps cards should be only in English whereas OPC is in either English and French. Interestingly, on the O-Pee-Chee cards, at times the information was different in English that is was in French. Many of my students don't even need ten months or just a year. They're off - integrated into American or Canadian society after a significantly shorter moments. Not with "perfect" English mind