Thank You for both of Your replies!
My initial thought was a flagpole too:)
Yes, that is the photo I was refering to, and yes it is on the right side of the bustle. I also found some other tanks ("DIXIE BELLE" and an unidentified one) from the same unit with this feature in Claude Gillino's book "First Blood US 1st AD in Tunisia". However many other Shermans on the period photos are lacking this item.