Back when Disney World opened, there was just the Magic Kingdom. Guests purchased coupon booklets. Each coupon was good for a different activity. One would permit all-day use of the transportation system. Then there would be other coupons with letters A-E. The letter represented a different type of ride. The E-ticket rides were the most popular (hence the name E-Ride Nights). You could purchase additional ride tickets without having to purchase another book. And, of course, there was a general admission coupon included in the booklet.
Sometime in the mid-70's, Disney introduced an Unlimited Passport that allowed admission and unlimited rides for a given number of days (usually 2 or 3 days). They still maintained the individual ticket books as well. Eventually, the ticket books were phased out and the World Passports went in to use shortly after EPCOT opened.
The tickets since then have gone by various names. The Super Pass, the Park Hopper, the Length of Stay Pass, the Unlimited Magic Pass and the Magic Your Way Pass are all names that Disney has used over time to describe their passes.
I'm not sure what kind of value Disney will place on the tickets that you purchased. I doubt that they have much in the way of a dollar credit towards today's admission media. It will be interesting to see how they treat them.
If you'd like to compare them to other tickets from the 70's, there's a pretty good page on Deb Wills' site:
http://allearsnet.com/tix/tixpix70.htm