Back in the pre-internet days, publicity was handled by mail-out. Much effort was expended to acquire a possibly overlapping group of addresses, such as the mailing list for another SF con a few states away, or a local comic-book store. The kind of one-sheet above would also be sent to local newspapers and even social clubs.
Here's an update from Dealers' Room chair David Means letting them know that a Thursday set-up is no longer in the works. Note the statement towards the end that SoonerCon might "make the Central Plaza our home in perpetuity." We are all lamenting that this did not come to pass. Maybe not all are lamenting.
Great art from Dell Harris for SoonerCon 3! It should be on a hundred dozen T-shirts! (This is a high-res scan from a photo print of the art.)
This is a version of the "Deadline Schedule" that supposedly guided the departments. If it was "X" months away from the Con, then x-y-z should have been completed by your department.
Happy New Year, see you soon I hope!