Chicago Cubs Sunoco Pins year of issue
 

Why are the Chicago Cubs pins from Sunoco listed as being from 1969 in the price guides?

The set includes Joe Pepitone. He didn't join the Cubs until July 29, 1970. These are more likely from 1971

I believe you are right about them being a 1971 issue, they were issued with the promo card for a Grand Opening Celebration in May, which couldn't be May 1970 because Pepitone was still an Astro then.