I don’t know specifically, but there are some clues, just from the artwork.
When Epcot opened in 1982, Disney changed their ticket media from the ticket book format to an all inclusive ticket. In the early 1980’s, these two park tickets were called World Passport tickets, and there were boxes on the ticket where a CM would hand stamp them with the date as you entered the park. The artwork on this button matches the artwork on the two park tickets from that era (One park tickets had either the castle or SSE, but not both).
My guess is that there was some sort of promotion related to the tickets, and this button was used to advertise it.