[JimNNN]

It would be very possible to replace one of the rivets on each side with a wingnut, after market. That could be what happened.

However, my owners manual says, "The lift gate has counterbalanced hinges and can be locked in the open position," and I can't see any other way it could be locked open. Looks like a different owner's manual than what you're showing, KULTULZ. Possibly a mid year change? I checked recently, and I think my wagon was made in June of '54. I'm posting pics from the manual and hopefully they'll be oriented correctly. I'll take pics of my hinges in the next day or two.