You have a distinctive insigne or "DI" (as referred to by collectors). They're authorized for units of battalion strength or larger. During the war they were worn on both lapels of the service tunic by enlisted personnel and centered on the shoulder strap by commissioned officers. Now worn on the shoulder strap by all grades. The principal color red indicates your subject was a member of either an artillery or engineer battalion (or regiment). The "rubbing" (?) you refer to is the manufacturer's mark.