1939 Kraft Mayo Label/Invitation

This is a weird one. My mom was looking through some old books, including a first edition of "The Prodigal Parents" by Sinclair Lewis, 1938. As she was thumbing through it, two Kraft mayonnaise labels fell out. It seems the Kraft-Phenix company, as it was called, used extra mayo labels as invitations to the company's first picnic at its San Francisco Bay Area plant. As you can see, the picnic was held on August 5, 1939 at La Honda Bowl. She has no idea where the labels/invites came from, let alone why there are two of them. I'm guessing they served lots of cheese and sandwiches slathered with Kraft mayonnaise at the picnic. For the record, I've always preferred Best Foods...