Just got an email from the owner who said they already got the truck with those hooks in place, back in '63 & never knew the purpose of them.

"Maybe he pulled a "Carl" and put them on upside down by mistake."
"Or, it could be for dragging people by their boot strings for asking one too many questions."
Which one was/is right?
I still like TUTS 59's suggestion:
Maybe it was to hang a sign, you did say it belonged to an Antique Shop ????