I paid $5 for the Muskogee card way back when.
The hand written note on it was written by Hertz at the time.

Later the Kattleman card was sent to me.
I scanned the cards together and wrote the hand written note between them as a note for me questioning the same thing you are asking about.

Later in conversations with Hertz, he was sure they were the same logo. He was privy to a lot more than I was in the Mason records like customer lists, etc.

That said. I believe the blue on the card could have been a mistake by an employee making $1 an hour or less in those days and he pulled green chips.

Mason sold both yellow and orange chips. I have both MSC yellow and orange. Is it age or usage that caused the difference? Reorders were not always listed in the cards we have.

Extensive search for orders of orange and green in the records we have access to today has not found further info on MSC reorders.

There is no research today (None-Nada-Zip) that can prove the MSC chips were ever used on salt water.