I'm not from that region of the country, but here's a link to Megafoods web site's history that shows it started 75 years ago and still exists corporately as "Consumers Cooperative Association":
http://www.megafoods.com/images/megaHistory.jpgWhile it doesn't mention the Indian Head Stamps, I suspect they were trading stamps similar to S&H, Plaid, Gold Bond, etc., for that region.
The only clue as to date that I can give is that the name of the Cooperative uses a 5-digit ZIP Code. Those 5-digit ZIP Codes started in 1963, so we know it has to be after that date, and the trading stamp promotions generally stalled later in that decade, so I'm guessing the example shown is probably mid-to-late 1960's.