Yes, I know...you've seen these a million times. Maybe you even have one of your own from when you were a Mark Twain "pilot" as a kid.
Look closely, though, this one is different: the date on the certificate is pre-dated "195__", which makes it exclusive to the park's opening years. Are there versions that are dated "196__"? I've never seen one; if you have, please let me know!
Most of these certficates read "19___", which places them later in the park's years or at least after 1959.
Are these still given away? Does the date now read "20__"?