Up thread, a FReeper in Pittsburgh had them.
There’s a cultural and linguistic divide in Pennsylvania. Pittsburgh is solidly in “pop” country, while eastern and central PA are part of “soda” land. Despite being in an “East Coast” state, Pittsburgh and environs are solidly part of the industrial Midwest. It may be a legacy of the time when rivers were used for transportation: most of eastern and central PA drains into the Atlantic by way of the Chesapeake Bay, while the rivers at Pittsburgh drain to the Gulf by way of the Ohio and Mississippi. Why this would extend to the reach of marketing of a type of folder sold to school children in the mid-20th century I don’t know.